21001555452 has 12 divisors (see below), whose sum is σ = 49003629416. Its totient is φ = 7000518480.

The previous prime is 21001555441. The next prime is 21001555469. The reversal of 21001555452 is 25455510012.

It is a tau number, because it is divible by the number of its divisors (12).

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, 875064799 + ... + 875064822.

Almost surely, 2^21001555452 is an apocalyptic number.

It is an amenable number.

21001555452 is an abundant number, since it is smaller than the sum of its proper divisors (28002073964).

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

21001555452 is a wasteful number, since it uses less digits than its factorization.

21001555452 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1750129628 (or 1750129626 counting only the distinct ones).

The product of its (nonzero) digits is 10000, while the sum is 30.

The spelling of 21001555452 in words is "twenty-one billion, one million, five hundred fifty-five thousand, four hundred fifty-two".