21491057376 has 480 divisors, whose sum is σ = 68625295200. Its totient is φ = 6584094720.

The previous prime is 21491057353. The next prime is 21491057381. The reversal of 21491057376 is 67375019412.

21491057376 is a `hidden beast` number, since 2 + 1 + 4 + 9 + 1 + 0 + 573 + 76 = 666.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 79 ways as a sum of consecutive naturals, for example, 197165610 + ... + 197165718.

It is an arithmetic number, because the mean of its divisors is an integer number (142969365).

Almost surely, 2^21491057376 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21491057376, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (34312647600).

21491057376 is an abundant number, since it is smaller than the sum of its proper divisors (47134237824).

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

21491057376 is a wasteful number, since it uses less digits than its factorization.

21491057376 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 264 (or 247 counting only the distinct ones).

The product of its (nonzero) digits is 317520, while the sum is 45.

The spelling of 21491057376 in words is "twenty-one billion, four hundred ninety-one million, fifty-seven thousand, three hundred seventy-six".