78990821 has 16 divisors (see below), whose sum is σ = 100359168. Its totient is φ = 60480000.

The previous prime is 78990817. The next prime is 78990827. The reversal of 78990821 is 12809987.

It is not a de Polignac number, because 78990821 - 2² = 78990817 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (78990827) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 11180 + ... + 16821.

It is an arithmetic number, because the mean of its divisors is an integer number (6272448).

Almost surely, 2^78990821 is an apocalyptic number.

It is an amenable number.

78990821 is a deficient number, since it is larger than the sum of its proper divisors (21368347).

78990821 is a wasteful number, since it uses less digits than its factorization.

78990821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 28052.

The product of its (nonzero) digits is 72576, while the sum is 44.

The square root of 78990821 is about 8887.6780432237. The cubic root of 78990821 is about 429.0674236521.

The spelling of 78990821 in words is "seventy-eight million, nine hundred ninety thousand, eight hundred twenty-one".