56611981 has 2 divisors, whose sum is σ = 56611982. Its totient is φ = 56611980.

The previous prime is 56611979. The next prime is 56611991. The reversal of 56611981 is 18911665.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 56025225 + 586756 = 7485^2 + 766^2 .

It is a cyclic number.

It is not a de Polignac number, because 56611981 - 2¹ = 56611979 is a prime.

It is a super-2 number, since 2×56611981² = 6409832785488722, which contains 22 as substring.

Together with 56611979, it forms a pair of twin primes.

It is a self number, because there is not a number n which added to its sum of digits gives 56611981.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (56611991) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 28305990 + 28305991.

It is an arithmetic number, because the mean of its divisors is an integer number (28305991).

Almost surely, 2^56611981 is an apocalyptic number.

It is an amenable number.

56611981 is a deficient number, since it is larger than the sum of its proper divisors (1).

56611981 is an equidigital number, since it uses as much as digits as its factorization.

56611981 is an evil number, because the sum of its binary digits is even.

The product of its digits is 12960, while the sum is 37.

The square root of 56611981 is about 7524.0933673101. The cubic root of 56611981 is about 383.9748541296.

The spelling of 56611981 in words is "fifty-six million, six hundred eleven thousand, nine hundred eighty-one".