21991258208 has 24 divisors (see below), whose sum is σ = 45842072472. Its totient is φ = 10348827136.

The previous prime is 21991258193. The next prime is 21991258229. The reversal of 21991258208 is 80285219912.

It is a happy number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 20212010 + ... + 20213097.

It is an arithmetic number, because the mean of its divisors is an integer number (1910086353).

Almost surely, 2^21991258208 is an apocalyptic number.

It is an amenable number.

21991258208 is an abundant number, since it is smaller than the sum of its proper divisors (23850814264).

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

21991258208 is a wasteful number, since it uses less digits than its factorization.

21991258208 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 40425134 (or 40425126 counting only the distinct ones).

The product of its (nonzero) digits is 207360, while the sum is 47.

The spelling of 21991258208 in words is "twenty-one billion, nine hundred ninety-one million, two hundred fifty-eight thousand, two hundred eight".