78931661 has 4 divisors (see below), whose sum is σ = 79372800. Its totient is φ = 78490524.

The previous prime is 78931631. The next prime is 78931667. The reversal of 78931661 is 16613987.

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 a de Polignac number, because none of the positive numbers 2^k-78931661 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 (78931667) 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, 220301 + ... + 220658.

It is an arithmetic number, because the mean of its divisors is an integer number (19843200).

Almost surely, 2^78931661 is an apocalyptic number.

It is an amenable number.

78931661 is a deficient number, since it is larger than the sum of its proper divisors (441139).

78931661 is a wasteful number, since it uses less digits than its factorization.

78931661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 441138.

The product of its digits is 54432, while the sum is 41.

The square root of 78931661 is about 8884.3492164592. The cubic root of 78931661 is about 428.9602805347.

The spelling of 78931661 in words is "seventy-eight million, nine hundred thirty-one thousand, six hundred sixty-one".