21621349764 has 189 divisors, whose sum is σ = 66162229077. Its totient is φ = 6161647968.

The previous prime is 21621349753. The next prime is 21621349769. The reversal of 21621349764 is 46794312612.

The square root of 21621349764 is 147042.

It is a perfect power (a square), and thus also a powerful number.

21621349764 is a `hidden beast` number, since 216 + 21 + 349 + 76 + 4 = 666.

It can be written as a sum of positive squares in only one way, i.e., 5103959364 + 16517390400 = 71442^2 + 128520^2 .

It is a tau number, because it is divible by the number of its divisors (189).

It is a nude number because it is divisible by every one of its digits.

It is not an unprimeable number, because it can be changed into a prime (21621349769) by changing a digit.

It is a polite number, since it can be written in 62 ways as a sum of consecutive naturals, for example, 55581682 + ... + 55582070.

Almost surely, 2^21621349764 is an apocalyptic number.

21621349764 is the 147042-nd square number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21621349764

21621349764 is an abundant number, since it is smaller than the sum of its proper divisors (44540879313).

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

21621349764 is an frugal number, since it uses more digits than its factorization.

21621349764 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 814 (or 401 counting only the distinct ones).

The product of its digits is 435456, while the sum is 45.

The spelling of 21621349764 in words is "twenty-one billion, six hundred twenty-one million, three hundred forty-nine thousand, seven hundred sixty-four".