21205272015 has 72 divisors (see below), whose sum is σ = 38412304560. Its totient is φ = 11099224800.

The previous prime is 21205272007. The next prime is 21205272017. The reversal of 21205272015 is 51027250212.

21205272015 is a `hidden beast` number, since 2 + 120 + 527 + 2 + 0 + 15 = 666.

It is not a de Polignac number, because 21205272015 - 2³ = 21205272007 is a prime.

It is a super-2 number, since 2×21205272015² (a number of 21 digits) contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a self number, because there is not a number n which added to its sum of digits gives 21205272015.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21205272017) by changing a digit.

It is a polite number, since it can be written in 71 ways as a sum of consecutive naturals, for example, 140432190 + ... + 140432340.

It is an arithmetic number, because the mean of its divisors is an integer number (533504230).

Almost surely, 2^21205272015 is an apocalyptic number.

21205272015 is a deficient number, since it is larger than the sum of its proper divisors (17207032545).

21205272015 is an frugal number, since it uses more digits than its factorization.

21205272015 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 482 (or 242 counting only the distinct ones).

The product of its (nonzero) digits is 2800, while the sum is 27.

The spelling of 21205272015 in words is "twenty-one billion, two hundred five million, two hundred seventy-two thousand, fifteen".