638420491 has 8 divisors (see below), whose sum is σ = 644194304. Its totient is φ = 632658600.

The previous prime is 638420483. The next prime is 638420513. The reversal of 638420491 is 194024836.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 638420491 - 2³ = 638420483 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 638420491.

It is not an unprimeable number, because it can be changed into a prime (638420401) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 131086 + ... + 135868.

It is an arithmetic number, because the mean of its divisors is an integer number (80524288).

Almost surely, 2^638420491 is an apocalyptic number.

638420491 is a deficient number, since it is larger than the sum of its proper divisors (5773813).

638420491 is a wasteful number, since it uses less digits than its factorization.

638420491 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5961.

The product of its (nonzero) digits is 41472, while the sum is 37.

The square root of 638420491 is about 25266.9842086467. The cubic root of 638420491 is about 861.0643442834.

The spelling of 638420491 in words is "six hundred thirty-eight million, four hundred twenty thousand, four hundred ninety-one".