21515012457 has 16 divisors (see below), whose sum is σ = 29111613120. Its totient is φ = 14132017152.

The previous prime is 21515012447. The next prime is 21515012459. The reversal of 21515012457 is 75421051512.

It is not a de Polignac number, because 21515012457 - 2¹⁰ = 21515011433 is a prime.

It is a super-2 number, since 2×21515012457² (a number of 21 digits) contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21515012459) 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, 66808 + ... + 217929.

It is an arithmetic number, because the mean of its divisors is an integer number (1819475820).

Almost surely, 2^21515012457 is an apocalyptic number.

It is an amenable number.

21515012457 is a deficient number, since it is larger than the sum of its proper divisors (7596600663).

21515012457 is a wasteful number, since it uses less digits than its factorization.

21515012457 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 285112.

The product of its (nonzero) digits is 14000, while the sum is 33.

Adding to 21515012457 its reverse (75421051512), we get a palindrome (96936063969).

The spelling of 21515012457 in words is "twenty-one billion, five hundred fifteen million, twelve thousand, four hundred fifty-seven".