78691021 has 4 divisors (see below), whose sum is σ = 79173952. Its totient is φ = 78208092.

The previous prime is 78690979. The next prime is 78691033. The reversal of 78691021 is 12019687.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 78691021 - 2⁷ = 78690893 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 (78691091) 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, 241221 + ... + 241546.

It is an arithmetic number, because the mean of its divisors is an integer number (19793488).

Almost surely, 2^78691021 is an apocalyptic number.

It is an amenable number.

78691021 is a deficient number, since it is larger than the sum of its proper divisors (482931).

78691021 is a wasteful number, since it uses less digits than its factorization.

78691021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 482930.

The product of its (nonzero) digits is 6048, while the sum is 34.

The square root of 78691021 is about 8870.7959620318. The cubic root of 78691021 is about 428.5239111497.

The spelling of 78691021 in words is "seventy-eight million, six hundred ninety-one thousand, twenty-one".