21621643452 has 36 divisors (see below), whose sum is σ = 54699220576. Its totient is φ = 7201344960.

The previous prime is 21621643369. The next prime is 21621643469. The reversal of 21621643452 is 25434612612.

21621643452 is a `hidden beast` number, since 2 + 1 + 6 + 2 + 1 + 643 + 4 + 5 + 2 = 666.

It is a tau number, because it is divible by the number of its divisors (36).

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 199633 + ... + 288264.

Almost surely, 2^21621643452 is an apocalyptic number.

It is an amenable number.

21621643452 is an abundant number, since it is smaller than the sum of its proper divisors (33077577124).

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

21621643452 is a wasteful number, since it uses less digits than its factorization.

21621643452 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 489138 (or 489133 counting only the distinct ones).

The product of its digits is 69120, while the sum is 36.

The spelling of 21621643452 in words is "twenty-one billion, six hundred twenty-one million, six hundred forty-three thousand, four hundred fifty-two".