66978931 has 2 divisors, whose sum is σ = 66978932. Its totient is φ = 66978930.

The previous prime is 66978881. The next prime is 66978937. The reversal of 66978931 is 13987966.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 66978931 - 2¹⁵ = 66946163 is a prime.

It is a super-2 number, since 2×66978931² = 8972354395805522, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (66978937) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 33489465 + 33489466.

It is an arithmetic number, because the mean of its divisors is an integer number (33489466).

Almost surely, 2^66978931 is an apocalyptic number.

66978931 is a deficient number, since it is larger than the sum of its proper divisors (1).

66978931 is an equidigital number, since it uses as much as digits as its factorization.

66978931 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 489888, while the sum is 49.

The square root of 66978931 is about 8184.0656766671. The cubic root of 66978931 is about 406.1122320703.

The spelling of 66978931 in words is "sixty-six million, nine hundred seventy-eight thousand, nine hundred thirty-one".