79810821 has 6 divisors (see below), whose sum is σ = 115282310. Its totient is φ = 53207208.

The previous prime is 79810817. The next prime is 79810837. The reversal of 79810821 is 12801897.

It can be written as a sum of positive squares in only one way, i.e., 74909025 + 4901796 = 8655^2 + 2214^2 .

It is not a de Polignac number, because 79810821 - 2² = 79810817 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (79817821) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 4433926 + ... + 4433943.

Almost surely, 2^79810821 is an apocalyptic number.

It is an amenable number.

79810821 is a deficient number, since it is larger than the sum of its proper divisors (35471489).

79810821 is a wasteful number, since it uses less digits than its factorization.

79810821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8867875 (or 8867872 counting only the distinct ones).

The product of its (nonzero) digits is 8064, while the sum is 36.

The square root of 79810821 is about 8933.6902229706. The cubic root of 79810821 is about 430.5470250970.

The spelling of 79810821 in words is "seventy-nine million, eight hundred ten thousand, eight hundred twenty-one".