21540991922 has 18 divisors (see below), whose sum is σ = 32887118943. Its totient is φ = 10581925884.

The previous prime is 21540991921. The next prime is 21540991931. The reversal of 21540991922 is 22919904512.

It can be written as a sum of positive squares in only one way, i.e., 10770495961 + 10770495961 = 103781^2 + 103781^2 .

It is an ABA number since it can be written as A⋅B^A, here for A=2, B=103781.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21540991921) by changing a digit.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 12245279 + ... + 12247037.

Almost surely, 2^21540991922 is an apocalyptic number.

21540991922 is a deficient number, since it is larger than the sum of its proper divisors (11346127021).

21540991922 is an frugal number, since it uses more digits than its factorization.

21540991922 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3638 (or 1820 counting only the distinct ones).

The product of its (nonzero) digits is 116640, while the sum is 44.

The spelling of 21540991922 in words is "twenty-one billion, five hundred forty million, nine hundred ninety-one thousand, nine hundred twenty-two".