• 70 can be written using four 4's:
70 has 8 divisors (see below), whose sum is σ = 144. Its totient is φ = 24.
The previous prime is 67. The next prime is 71. The reversal of 70 is 7.
It is a happy number.
70 is nontrivially palindromic in base 9 and base 13.
70 is an esthetic number in base 3 and base 4, because in such bases its adjacent digits differ by 1.
70 is a nontrivial binomial coefficient, being equal to C(8, 4).
It is a sliding number, since 70 = 20 + 50 and 1/20 + 1/50 = 0.070.
It is a sphenic number, since it is the product of 3 distinct primes.
70 is an admirable number.
It is a Harshad number since it is a multiple of its sum of digits (7).
It is a super Niven number, because it is divisible the sum of any subset of its (nonzero) digits.
70 is an idoneal number.
It is a magnanimous number.
It is an alternating number because its digits alternate between odd and even.
70 is an undulating number in base 3.
70 is a nontrivial repdigit in base 9 and base 13.
It is a plaindrome in base 9, base 12, base 13, base 15 and base 16.
It is a nialpdrome in base 9, base 10, base 11, base 13 and base 14.
It is a zygodrome in base 9 and base 13.
It is a congruent number.
It is a pernicious number, because its binary representation contains a prime number (3) of ones.
It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 7 + ... + 13.
It is an arithmetic number, because the mean of its divisors is an integer number (18).
70 is the 7-th pentagonal number.
70 is a primitive abundant number, since it is smaller than the sum of its proper divisors, none of which is abundant.
It is a weird number, because it is abundant, but not a pseudoperfect number.
It is a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (72).
70 is a wasteful number, since it uses less digits than its factorization.
70 is an odious number, because the sum of its binary digits is odd.
The sum of its prime factors is 14.
The product of its (nonzero) digits is 7, while the sum is 7.
The square root of 70 is about 8.3666002653. The cubic root of 70 is about 4.1212852998.
The spelling of 70 in words is "seventy", and thus it is an aban number, an iban number, an oban number, and an uban number.
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