21551501540 has 24 divisors (see below), whose sum is σ = 45260997432. Its totient is φ = 8620058880.

The previous prime is 21551501527. The next prime is 21551501581. The reversal of 21551501540 is 4510515512.

It can be written as a sum of positive squares in 4 ways, for example, as 2221048384 + 19330453156 = 47128^2 + 139034^2 .

It is an unprimeable number.

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 7 ways as a sum of consecutive naturals, for example, 490142 + ... + 532298.

It is an arithmetic number, because the mean of its divisors is an integer number (1885874893).

Almost surely, 2^21551501540 is an apocalyptic number.

21551501540 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21551501540 is an abundant number, since it is smaller than the sum of its proper divisors (23709495892).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21551501540 is a wasteful number, since it uses less digits than its factorization.

21551501540 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 67727 (or 67725 counting only the distinct ones).

The product of its (nonzero) digits is 5000, while the sum is 29.

The spelling of 21551501540 in words is "twenty-one billion, five hundred fifty-one million, five hundred one thousand, five hundred forty".