21091911456 has 192 divisors, whose sum is σ = 69132994560. Its totient is φ = 5470095360.

The previous prime is 21091911443. The next prime is 21091911469. The reversal of 21091911456 is 65411919012.

It is an interprime number because it is at equal distance from previous prime (21091911443) and next prime (21091911469).

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 5978365 + ... + 5981891.

It is an arithmetic number, because the mean of its divisors is an integer number (360067680).

Almost surely, 2^21091911456 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 21091911456, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (34566497280).

21091911456 is an abundant number, since it is smaller than the sum of its proper divisors (48041083104).

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

21091911456 is a wasteful number, since it uses less digits than its factorization.

21091911456 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4367 (or 4359 counting only the distinct ones).

The product of its (nonzero) digits is 19440, while the sum is 39.

The spelling of 21091911456 in words is "twenty-one billion, ninety-one million, nine hundred eleven thousand, four hundred fifty-six".