21121716651 has 32 divisors (see below), whose sum is σ = 32627865600. Its totient is φ = 11904330240.

The previous prime is 21121716601. The next prime is 21121716667. The reversal of 21121716651 is 15661712112.

It is not a de Polignac number, because 21121716651 - 2²⁵ = 21088162219 is a prime.

It is a super-2 number, since 2×21121716651² (a number of 21 digits) contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21121716601) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 750606 + ... + 778236.

It is an arithmetic number, because the mean of its divisors is an integer number (1019620800).

Almost surely, 2^21121716651 is an apocalyptic number.

21121716651 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

21121716651 is a deficient number, since it is larger than the sum of its proper divisors (11506148949).

21121716651 is a wasteful number, since it uses less digits than its factorization.

21121716651 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 28139.

The product of its digits is 5040, while the sum is 33.

The spelling of 21121716651 in words is "twenty-one billion, one hundred twenty-one million, seven hundred sixteen thousand, six hundred fifty-one".