78661931 has 4 divisors (see below), whose sum is σ = 79440864. Its totient is φ = 77883000.

The previous prime is 78661853. The next prime is 78661937. The reversal of 78661931 is 13916687.

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 78661931 - 2¹⁸ = 78399787 is a prime.

It is a super-2 number, since 2×78661931² = 12375398777297522, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (78661937) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 389315 + ... + 389516.

It is an arithmetic number, because the mean of its divisors is an integer number (19860216).

Almost surely, 2^78661931 is an apocalyptic number.

78661931 is a deficient number, since it is larger than the sum of its proper divisors (778933).

78661931 is a wasteful number, since it uses less digits than its factorization.

78661931 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 778932.

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

The square root of 78661931 is about 8869.1561605375. The cubic root of 78661931 is about 428.4710999699.

The spelling of 78661931 in words is "seventy-eight million, six hundred sixty-one thousand, nine hundred thirty-one".