51691961 has 2 divisors, whose sum is σ = 51691962. Its totient is φ = 51691960.

The previous prime is 51691933. The next prime is 51691987. The reversal of 51691961 is 16919615.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 47004736 + 4687225 = 6856^2 + 2165^2 .

It is a cyclic number.

It is not a de Polignac number, because 51691961 - 2⁶ = 51691897 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (51691061) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 25845980 + 25845981.

It is an arithmetic number, because the mean of its divisors is an integer number (25845981).

Almost surely, 2^51691961 is an apocalyptic number.

It is an amenable number.

51691961 is a deficient number, since it is larger than the sum of its proper divisors (1).

51691961 is an equidigital number, since it uses as much as digits as its factorization.

51691961 is an evil number, because the sum of its binary digits is even.

The product of its digits is 14580, while the sum is 38.

The square root of 51691961 is about 7189.7121639187. The cubic root of 51691961 is about 372.5126305343.

The spelling of 51691961 in words is "fifty-one million, six hundred ninety-one thousand, nine hundred sixty-one".