21510660021 has 16 divisors (see below), whose sum is σ = 28912363200. Its totient is φ = 14225126400.

The previous prime is 21510660011. The next prime is 21510660023. The reversal of 21510660021 is 12006601512.

It is not a de Polignac number, because 21510660021 - 2¹⁵ = 21510627253 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21510659973 and 21510660000.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21510660023) 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, 148846 + ... + 255296.

It is an arithmetic number, because the mean of its divisors is an integer number (1807022700).

Almost surely, 2^21510660021 is an apocalyptic number.

It is an amenable number.

21510660021 is a deficient number, since it is larger than the sum of its proper divisors (7401703179).

21510660021 is a wasteful number, since it uses less digits than its factorization.

21510660021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 106996.

The product of its (nonzero) digits is 720, while the sum is 24.

The spelling of 21510660021 in words is "twenty-one billion, five hundred ten million, six hundred sixty thousand, twenty-one".