56639981 has 2 divisors, whose sum is σ = 56639982. Its totient is φ = 56639980.

The previous prime is 56639963. The next prime is 56640011. The reversal of 56639981 is 18993665.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 50055625 + 6584356 = 7075^2 + 2566^2 .

It is a cyclic number.

It is not a de Polignac number, because 56639981 - 2¹⁰ = 56638957 is a prime.

It is a super-3 number, since 3×56639981³ (a number of 24 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is a Sophie Germain prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (56639951) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 28319990 + 28319991.

It is an arithmetic number, because the mean of its divisors is an integer number (28319991).

Almost surely, 2^56639981 is an apocalyptic number.

It is an amenable number.

56639981 is a deficient number, since it is larger than the sum of its proper divisors (1).

56639981 is an equidigital number, since it uses as much as digits as its factorization.

56639981 is an evil number, because the sum of its binary digits is even.

The product of its digits is 349920, while the sum is 47.

The square root of 56639981 is about 7525.9538265923. The cubic root of 56639981 is about 384.0381477039.

The spelling of 56639981 in words is "fifty-six million, six hundred thirty-nine thousand, nine hundred eighty-one".