21295790640 has 120 divisors (see below), whose sum is σ = 71593498080. Its totient is φ = 5672911872.

The previous prime is 21295790629. The next prime is 21295790669. The reversal of 21295790640 is 4609759212.

21295790640 is a `hidden beast` number, since 2 + 12 + 9 + 579 + 0 + 64 + 0 = 666.

It is a tau number, because it is divible by the number of its divisors (120).

It is a Harshad number since it is a multiple of its sum of digits (45).

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 692716 + ... + 722804.

It is an arithmetic number, because the mean of its divisors is an integer number (596612484).

Almost surely, 2^21295790640 is an apocalyptic number.

21295790640 is a gapful number since it is divisible by the number (20) 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 21295790640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (35796749040).

21295790640 is an abundant number, since it is smaller than the sum of its proper divisors (50297707440).

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

21295790640 is a wasteful number, since it uses less digits than its factorization.

21295790640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 31091 (or 31082 counting only the distinct ones).

The product of its (nonzero) digits is 272160, while the sum is 45.

The spelling of 21295790640 in words is "twenty-one billion, two hundred ninety-five million, seven hundred ninety thousand, six hundred forty".