56721994921 has 2 divisors, whose sum is σ = 56721994922. Its totient is φ = 56721994920.

The previous prime is 56721994897. The next prime is 56721994943. The reversal of 56721994921 is 12949912765.

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., 46001670400 + 10720324521 = 214480^2 + 103539^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-56721994921 is a prime.

It is not a weakly prime, because it can be changed into another prime (56721944921) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 28360997460 + 28360997461.

It is an arithmetic number, because the mean of its divisors is an integer number (28360997461).

Almost surely, 2^56721994921 is an apocalyptic number.

It is an amenable number.

56721994921 is a deficient number, since it is larger than the sum of its proper divisors (1).

56721994921 is an equidigital number, since it uses as much as digits as its factorization.

56721994921 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2449440, while the sum is 55.

The spelling of 56721994921 in words is "fifty-six billion, seven hundred twenty-one million, nine hundred ninety-four thousand, nine hundred twenty-one".