636430981 has 2 divisors, whose sum is σ = 636430982. Its totient is φ = 636430980.

The previous prime is 636430967. The next prime is 636431021. The reversal of 636430981 is 189034636.

It is an a-pointer prime, because the next prime (636431021) can be obtained adding 636430981 to its sum of digits (40).

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 520524225 + 115906756 = 22815^2 + 10766^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-636430981 is a prime.

It is a super-2 number, since 2×636430981² = 810088787153244722, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (636430381) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 318215490 + 318215491.

It is an arithmetic number, because the mean of its divisors is an integer number (318215491).

Almost surely, 2^636430981 is an apocalyptic number.

It is an amenable number.

636430981 is a deficient number, since it is larger than the sum of its proper divisors (1).

636430981 is an equidigital number, since it uses as much as digits as its factorization.

636430981 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 93312, while the sum is 40.

The square root of 636430981 is about 25227.5837328905. The cubic root of 636430981 is about 860.1689685124.

The spelling of 636430981 in words is "six hundred thirty-six million, four hundred thirty thousand, nine hundred eighty-one".