638340921 has 12 divisors (see below), whose sum is σ = 930666672. Its totient is φ = 421582776.

The previous prime is 638340889. The next prime is 638340943. The reversal of 638340921 is 129043836.

It is not a de Polignac number, because 638340921 - 2⁵ = 638340889 is a prime.

It is not an unprimeable number, because it can be changed into a prime (638340961) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 330471 + ... + 332396.

It is an arithmetic number, because the mean of its divisors is an integer number (77555556).

Almost surely, 2^638340921 is an apocalyptic number.

It is an amenable number.

638340921 is a deficient number, since it is larger than the sum of its proper divisors (292325751).

638340921 is a wasteful number, since it uses less digits than its factorization.

638340921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 662980 (or 662977 counting only the distinct ones).

The product of its (nonzero) digits is 31104, while the sum is 36.

The square root of 638340921 is about 25265.4095751484. The cubic root of 638340921 is about 861.0285696712.

The spelling of 638340921 in words is "six hundred thirty-eight million, three hundred forty thousand, nine hundred twenty-one".