638403851 has 4 divisors (see below), whose sum is σ = 644985432. Its totient is φ = 631822272.

The previous prime is 638403827. The next prime is 638403881. The reversal of 638403851 is 158304836.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 638403851 - 2²⁶ = 571294987 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (638403811) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3290645 + ... + 3290838.

It is an arithmetic number, because the mean of its divisors is an integer number (161246358).

Almost surely, 2^638403851 is an apocalyptic number.

638403851 is a deficient number, since it is larger than the sum of its proper divisors (6581581).

638403851 is an equidigital number, since it uses as much as digits as its factorization.

638403851 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6581580.

The product of its (nonzero) digits is 69120, while the sum is 38.

The square root of 638403851 is about 25266.6549230404. The cubic root of 638403851 is about 861.0568631978.

The spelling of 638403851 in words is "six hundred thirty-eight million, four hundred three thousand, eight hundred fifty-one".