21761688921 has 16 divisors (see below), whose sum is σ = 33176444928. Its totient is φ = 12429334800.

The previous prime is 21761688919. The next prime is 21761688959. The reversal of 21761688921 is 12988616712.

It is not a de Polignac number, because 21761688921 - 2¹ = 21761688919 is a prime.

It is a super-2 number, since 2×21761688921² (a number of 21 digits) contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21761688521) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 201115 + ... + 289776.

It is an arithmetic number, because the mean of its divisors is an integer number (2073527808).

Almost surely, 2^21761688921 is an apocalyptic number.

21761688921 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

21761688921 is a deficient number, since it is larger than the sum of its proper divisors (11414756007).

21761688921 is a wasteful number, since it uses less digits than its factorization.

21761688921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 493012.

The product of its digits is 580608, while the sum is 51.

The spelling of 21761688921 in words is "twenty-one billion, seven hundred sixty-one million, six hundred eighty-eight thousand, nine hundred twenty-one".