78621251 has 4 divisors (see below), whose sum is σ = 78658992. Its totient is φ = 78583512.

The previous prime is 78621203. The next prime is 78621281. The reversal of 78621251 is 15212687.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 78621251 - 2¹⁸ = 78359107 is a prime.

It is a super-2 number, since 2×78621251² = 12362602217610002, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (78621281) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 15551 + ... + 19976.

It is an arithmetic number, because the mean of its divisors is an integer number (19664748).

Almost surely, 2^78621251 is an apocalyptic number.

78621251 is a deficient number, since it is larger than the sum of its proper divisors (37741).

78621251 is a wasteful number, since it uses less digits than its factorization.

78621251 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 37740.

The product of its digits is 6720, while the sum is 32.

The square root of 78621251 is about 8866.8625228995. The cubic root of 78621251 is about 428.3972259894.

The spelling of 78621251 in words is "seventy-eight million, six hundred twenty-one thousand, two hundred fifty-one".