51256721 has 2 divisors, whose sum is σ = 51256722. Its totient is φ = 51256720.

The previous prime is 51256703. The next prime is 51256727. The reversal of 51256721 is 12765215.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 31764496 + 19492225 = 5636^2 + 4415^2 .

It is a cyclic number.

It is not a de Polignac number, because 51256721 - 2²² = 47062417 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (51256727) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 25628360 + 25628361.

It is an arithmetic number, because the mean of its divisors is an integer number (25628361).

Almost surely, 2^51256721 is an apocalyptic number.

It is an amenable number.

51256721 is a deficient number, since it is larger than the sum of its proper divisors (1).

51256721 is an equidigital number, since it uses as much as digits as its factorization.

51256721 is an evil number, because the sum of its binary digits is even.

The product of its digits is 4200, while the sum is 29.

The square root of 51256721 is about 7159.3799312510. The cubic root of 51256721 is about 371.4641787715.

The spelling of 51256721 in words is "fifty-one million, two hundred fifty-six thousand, seven hundred twenty-one".