21651404508 has 18 divisors (see below), whose sum is σ = 54729939264. Its totient is φ = 7217134824.

The previous prime is 21651404503. The next prime is 21651404519. The reversal of 21651404508 is 80540415612.

It is a happy number.

21651404508 is a `hidden beast` number, since 2 + 1 + 6 + 5 + 140 + 4 + 508 = 666.

It is a tau number, because it is divible by the number of its divisors (18).

It is a Harshad number since it is a multiple of its sum of digits (36), and also a Moran number because the ratio is a prime number: 601427903 = 21651404508 / (2 + 1 + 6 + 5 + 1 + 4 + 0 + 4 + 5 + 0 + 8).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21651404503) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 300713916 + ... + 300713987.

Almost surely, 2^21651404508 is an apocalyptic number.

It is an amenable number.

21651404508 is an abundant number, since it is smaller than the sum of its proper divisors (33078534756).

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

21651404508 is a wasteful number, since it uses less digits than its factorization.

21651404508 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 601427913 (or 601427908 counting only the distinct ones).

The product of its (nonzero) digits is 38400, while the sum is 36.

The spelling of 21651404508 in words is "twenty-one billion, six hundred fifty-one million, four hundred four thousand, five hundred eight".