638725987 has 2 divisors, whose sum is σ = 638725988. Its totient is φ = 638725986.

The previous prime is 638725963. The next prime is 638725993. The reversal of 638725987 is 789527836.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 638725987 - 2⁷ = 638725859 is a prime.

It is not a weakly prime, because it can be changed into another prime (638725687) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 319362993 + 319362994.

It is an arithmetic number, because the mean of its divisors is an integer number (319362994).

Almost surely, 2^638725987 is an apocalyptic number.

638725987 is a deficient number, since it is larger than the sum of its proper divisors (1).

638725987 is an equidigital number, since it uses as much as digits as its factorization.

638725987 is an evil number, because the sum of its binary digits is even.

The product of its digits is 5080320, while the sum is 55.

The square root of 638725987 is about 25273.0288449960. The cubic root of 638725987 is about 861.2016674476.

The spelling of 638725987 in words is "six hundred thirty-eight million, seven hundred twenty-five thousand, nine hundred eighty-seven".