21070 has 24 divisors (see below), whose sum is σ = 45144. Its totient is φ = 7056.

The previous prime is 21067. The next prime is 21089. The reversal of 21070 is 7012.

It is a Harshad number since it is a multiple of its sum of digits (10).

It is an alternating number because its digits alternate between even and odd.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 469 + ... + 511.

It is an arithmetic number, because the mean of its divisors is an integer number (1881).

2²¹⁰⁷⁰ is an apocalyptic number.

21070 is an abundant number, since it is smaller than the sum of its proper divisors (24074).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

It is a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (22572).

21070 is a wasteful number, since it uses less digits than its factorization.

21070 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 64 (or 57 counting only the distinct ones).

The product of its (nonzero) digits is 14, while the sum is 10.

The square root of 21070 is about 145.1550894733. The cubic root of 21070 is about 27.6198624790.

Adding to 21070 its reverse (7012), we get a palindrome (28082).

The spelling of 21070 in words is "twenty-one thousand, seventy", and thus it is an iban number.