63640981 has 2 divisors, whose sum is σ = 63640982. Its totient is φ = 63640980.

The previous prime is 63640939. The next prime is 63641033. The reversal of 63640981 is 18904636.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 57138481 + 6502500 = 7559^2 + 2550^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-63640981 is a prime.

It is a super-2 number, since 2×63640981² = 8100348925284722, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 63640981.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (63640901) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 31820490 + 31820491.

It is an arithmetic number, because the mean of its divisors is an integer number (31820491).

Almost surely, 2^63640981 is an apocalyptic number.

It is an amenable number.

63640981 is a deficient number, since it is larger than the sum of its proper divisors (1).

63640981 is an equidigital number, since it uses as much as digits as its factorization.

63640981 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 31104, while the sum is 37.

The square root of 63640981 is about 7977.5297555070. The cubic root of 63640981 is about 399.2506407785.

The spelling of 63640981 in words is "sixty-three million, six hundred forty thousand, nine hundred eighty-one".