6521912640 has 840 divisors, whose sum is σ = 26557495272. Its totient is φ = 1512898560.

The previous prime is 6521912581. The next prime is 6521912699. The reversal of 6521912640 is 462191256.

6521912640 is a `hidden beast` number, since 6 + 5 + 2 + 1 + 9 + 1 + 2 + 640 = 666.

It is an interprime number because it is at equal distance from previous prime (6521912581) and next prime (6521912699).

It can be written as a sum of positive squares in 4 ways, for example, as 226442304 + 6295470336 = 15048^2 + 79344^2 .

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 = 6521912595 and 6521912604.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 119 ways as a sum of consecutive naturals, for example, 159071020 + ... + 159071060.

Almost surely, 2^6521912640 is an apocalyptic number.

6521912640 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 6521912640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (13278747636).

6521912640 is an abundant number, since it is smaller than the sum of its proper divisors (20035582632).

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

6521912640 is a wasteful number, since it uses less digits than its factorization.

6521912640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 125 (or 87 counting only the distinct ones).

The product of its (nonzero) digits is 25920, while the sum is 36.

The square root of 6521912640 is about 80758.3595672919. The cubic root of 6521912640 is about 1868.3503844720.

The spelling of 6521912640 in words is "six billion, five hundred twenty-one million, nine hundred twelve thousand, six hundred forty".