639925440 has 336 divisors, whose sum is σ = 2555540736. Its totient is φ = 132802560.

The previous prime is 639925423. The next prime is 639925457. The reversal of 639925440 is 44529936.

It is an interprime number because it is at equal distance from previous prime (639925423) and next prime (639925457).

It is a tau number, because it is divible by the number of its divisors (336).

It is a Harshad number since it is a multiple of its sum of digits (42).

It is a junction number, because it is equal to n+sod(n) for n = 639925392 and 639925401.

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 812727 + ... + 813513.

It is an arithmetic number, because the mean of its divisors is an integer number (7605776).

Almost surely, 2^639925440 is an apocalyptic number.

639925440 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 639925440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1277770368).

639925440 is an abundant number, since it is smaller than the sum of its proper divisors (1915615296).

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

639925440 is a wasteful number, since it uses less digits than its factorization.

639925440 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 836 (or 815 counting only the distinct ones).

The product of its (nonzero) digits is 233280, while the sum is 42.

The square root of 639925440 is about 25296.7476170357. The cubic root of 639925440 is about 861.7404091609.

The spelling of 639925440 in words is "six hundred thirty-nine million, nine hundred twenty-five thousand, four hundred forty".