638439651 has 10 divisors (see below), whose sum is σ = 953718612. Its totient is φ = 425626380.

The previous prime is 638439647. The next prime is 638439661. The reversal of 638439651 is 156934836.

638439651 is a `hidden beast` number, since 638 + 4 + 3 + 9 + 6 + 5 + 1 = 666.

It is not a de Polignac number, because 638439651 - 2² = 638439647 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 638439597 and 638439606.

It is not an unprimeable number, because it can be changed into a prime (638439661) by changing a digit.

It is a polite number, since it can be written in 9 ways as a sum of consecutive naturals, for example, 3940905 + ... + 3941066.

Almost surely, 2^638439651 is an apocalyptic number.

638439651 is a deficient number, since it is larger than the sum of its proper divisors (315278961).

638439651 is an equidigital number, since it uses as much as digits as its factorization.

638439651 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7881983 (or 7881974 counting only the distinct ones).

The product of its digits is 466560, while the sum is 45.

The square root of 638439651 is about 25267.3633567098. The cubic root of 638439651 is about 861.0729581610.

The spelling of 638439651 in words is "six hundred thirty-eight million, four hundred thirty-nine thousand, six hundred fifty-one".