664251840 has 420 divisors, whose sum is σ = 2753889336. Its totient is φ = 151538688.

The previous prime is 664251823. The next prime is 664251853. The reversal of 664251840 is 48152466.

664251840 is a `hidden beast` number, since 6 + 642 + 5 + 1 + 8 + 4 + 0 = 666.

It is a tau number, because it is divible by the number of its divisors (420).

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a junction number, because it is equal to n+sod(n) for n = 664251795 and 664251804.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 59 ways as a sum of consecutive naturals, for example, 1269819 + ... + 1270341.

Almost surely, 2^664251840 is an apocalyptic number.

664251840 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 664251840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1376944668).

664251840 is an abundant number, since it is smaller than the sum of its proper divisors (2089637496).

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

664251840 is a wasteful number, since it uses less digits than its factorization.

664251840 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 566 (or 540 counting only the distinct ones).

The product of its (nonzero) digits is 46080, while the sum is 36.

The square root of 664251840 is about 25773.0836338999. The cubic root of 664251840 is about 872.5244159198.

It can be divided in two parts, 66425 and 1840, that added together give a triangular number (68265 = T₃₆₉).

The spelling of 664251840 in words is "six hundred sixty-four million, two hundred fifty-one thousand, eight hundred forty".