638345490 has 64 divisors (see below), whose sum is σ = 1591529472. Its totient is φ = 163684800.

The previous prime is 638345467. The next prime is 638345501. The reversal of 638345490 is 94543836.

It is an alternating number because its digits alternate between even and odd.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 149485 + ... + 153695.

It is an arithmetic number, because the mean of its divisors is an integer number (24867648).

Almost surely, 2^638345490 is an apocalyptic number.

It is a pronic number, being equal to 25265×25266.

It is a practical number, because each smaller number is the sum of distinct divisors of 638345490, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (795764736).

638345490 is an abundant number, since it is smaller than the sum of its proper divisors (953183982).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

638345490 is a wasteful number, since it uses less digits than its factorization.

638345490 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4415.

The product of its (nonzero) digits is 311040, while the sum is 42.

The square root of 638345490 is about 25265.4999950525. The cubic root of 638345490 is about 861.0306239706.

The spelling of 638345490 in words is "six hundred thirty-eight million, three hundred forty-five thousand, four hundred ninety".