63815981 has 2 divisors, whose sum is σ = 63815982. Its totient is φ = 63815980.

The previous prime is 63815971. The next prime is 63816001. The reversal of 63815981 is 18951836.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 36421225 + 27394756 = 6035^2 + 5234^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-63815981 is a prime.

It is a super-2 number, since 2×63815981² = 8144958861984722, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (63815911) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 31907990 + 31907991.

It is an arithmetic number, because the mean of its divisors is an integer number (31907991).

Almost surely, 2^63815981 is an apocalyptic number.

It is an amenable number.

63815981 is a deficient number, since it is larger than the sum of its proper divisors (1).

63815981 is an equidigital number, since it uses as much as digits as its factorization.

63815981 is an evil number, because the sum of its binary digits is even.

The product of its digits is 51840, while the sum is 41.

The square root of 63815981 is about 7988.4905332610. The cubic root of 63815981 is about 399.6162590583.

The spelling of 63815981 in words is "sixty-three million, eight hundred fifteen thousand, nine hundred eighty-one".