639407730 has 128 divisors (see below), whose sum is σ = 1723373568. Its totient is φ = 150792192.

The previous prime is 639407729. The next prime is 639407731. The reversal of 639407730 is 37704936.

It is an interprime number because it is at equal distance from previous prime (639407729) and next prime (639407731).

It is a Harshad number since it is a multiple of its sum of digits (39).

It is not an unprimeable number, because it can be changed into a prime (639407731) by changing a digit.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 1053087 + ... + 1053693.

It is an arithmetic number, because the mean of its divisors is an integer number (13463856).

Almost surely, 2^639407730 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 639407730, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (861686784).

639407730 is an abundant number, since it is smaller than the sum of its proper divisors (1083965838).

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

639407730 is a wasteful number, since it uses less digits than its factorization.

639407730 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 740.

The product of its (nonzero) digits is 95256, while the sum is 39.

The square root of 639407730 is about 25286.5128082146. The cubic root of 639407730 is about 861.5079591687.

The spelling of 639407730 in words is "six hundred thirty-nine million, four hundred seven thousand, seven hundred thirty".