51621931 has 2 divisors, whose sum is σ = 51621932. Its totient is φ = 51621930.

The previous prime is 51621929. The next prime is 51621949. The reversal of 51621931 is 13912615.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 51621931 - 2¹ = 51621929 is a prime.

It is a super-2 number, since 2×51621931² = 5329647520337522, which contains 22 as substring.

Together with 51621929, it forms a pair of twin primes.

It is equal to p_3092545 and since 51621931 and 3092545 have the same sum of digits, it is a Honaker prime.

It is a self number, because there is not a number n which added to its sum of digits gives 51621931.

It is not a weakly prime, because it can be changed into another prime (51621901) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 25810965 + 25810966.

It is an arithmetic number, because the mean of its divisors is an integer number (25810966).

Almost surely, 2^51621931 is an apocalyptic number.

51621931 is a deficient number, since it is larger than the sum of its proper divisors (1).

51621931 is an equidigital number, since it uses as much as digits as its factorization.

51621931 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1620, while the sum is 28.

The square root of 51621931 is about 7184.8403600915. The cubic root of 51621931 is about 372.3443332567.

The spelling of 51621931 in words is "fifty-one million, six hundred twenty-one thousand, nine hundred thirty-one".