21251720484 has 36 divisors (see below), whose sum is σ = 53754582336. Its totient is φ = 7079297328.

The previous prime is 21251720461. The next prime is 21251720491. The reversal of 21251720484 is 48402715212.

21251720484 is a `hidden beast` number, since 2 + 1 + 2 + 5 + 172 + 0 + 484 = 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 an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 135744 + ... + 246839.

Almost surely, 2^21251720484 is an apocalyptic number.

It is an amenable number.

21251720484 is an abundant number, since it is smaller than the sum of its proper divisors (32502861852).

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

21251720484 is a wasteful number, since it uses less digits than its factorization.

21251720484 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 384136 (or 384131 counting only the distinct ones).

The product of its (nonzero) digits is 35840, while the sum is 36.

The spelling of 21251720484 in words is "twenty-one billion, two hundred fifty-one million, seven hundred twenty thousand, four hundred eighty-four".