21555538015 has 16 divisors (see below), whose sum is σ = 29445037056. Its totient is φ = 14995156000.

The previous prime is 21555538009. The next prime is 21555538091. The reversal of 21555538015 is 51083555512.

It is not a de Polignac number, because 21555538015 - 2¹³ = 21555529823 is a prime.

It is a super-2 number, since 2×21555538015² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 8518711 + ... + 8521240.

It is an arithmetic number, because the mean of its divisors is an integer number (1840314816).

Almost surely, 2^21555538015 is an apocalyptic number.

21555538015 is a deficient number, since it is larger than the sum of its proper divisors (7889499041).

21555538015 is a wasteful number, since it uses less digits than its factorization.

21555538015 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 17039990.

The product of its (nonzero) digits is 150000, while the sum is 40.

The spelling of 21555538015 in words is "twenty-one billion, five hundred fifty-five million, five hundred thirty-eight thousand, fifteen".