21507621653 has 16 divisors (see below), whose sum is σ = 25897173120. Its totient is φ = 17449079616.

The previous prime is 21507621647. The next prime is 21507621677. The reversal of 21507621653 is 35612670512.

It is a happy number.

It is a cyclic number.

It is not a de Polignac number, because 21507621653 - 2⁶ = 21507621589 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21507621623) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 76175 + ... + 220947.

It is an arithmetic number, because the mean of its divisors is an integer number (1618573320).

Almost surely, 2^21507621653 is an apocalyptic number.

It is an amenable number.

21507621653 is a deficient number, since it is larger than the sum of its proper divisors (4389551467).

21507621653 is a wasteful number, since it uses less digits than its factorization.

21507621653 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 145916.

The product of its (nonzero) digits is 75600, while the sum is 38.

The spelling of 21507621653 in words is "twenty-one billion, five hundred seven million, six hundred twenty-one thousand, six hundred fifty-three".