51556721 has 16 divisors (see below), whose sum is σ = 54432000. Its totient is φ = 48787200.

The previous prime is 51556717. The next prime is 51556787. The reversal of 51556721 is 12765515.

It is a cyclic number.

It is not a de Polignac number, because 51556721 - 2² = 51556717 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (51556621) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 258980 + ... + 259178.

It is an arithmetic number, because the mean of its divisors is an integer number (3402000).

Almost surely, 2^51556721 is an apocalyptic number.

It is an amenable number.

51556721 is a deficient number, since it is larger than the sum of its proper divisors (2875279).

51556721 is a wasteful number, since it uses less digits than its factorization.

51556721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 400.

The product of its digits is 10500, while the sum is 32.

The square root of 51556721 is about 7180.3008989875. The cubic root of 51556721 is about 372.1874825758.

The spelling of 51556721 in words is "fifty-one million, five hundred fifty-six thousand, seven hundred twenty-one".