21512501105551 has 16 divisors (see below), whose sum is σ = 23346801974880. Its totient is φ = 19747390924800.

The previous prime is 21512501105531. The next prime is 21512501105609. The reversal of 21512501105551 is 15550110521512.

It is a cyclic number.

It is not a de Polignac number, because 21512501105551 - 2²⁹ = 21511964234639 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21512501105531) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 93385866 + ... + 93615943.

It is an arithmetic number, because the mean of its divisors is an integer number (1459175123430).

Almost surely, 2^{21512501105551} is an apocalyptic number.

21512501105551 is a deficient number, since it is larger than the sum of its proper divisors (1834300869329).

21512501105551 is a wasteful number, since it uses less digits than its factorization.

21512501105551 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 187001994.

The product of its (nonzero) digits is 12500, while the sum is 34.

The spelling of 21512501105551 in words is "twenty-one trillion, five hundred twelve billion, five hundred one million, one hundred five thousand, five hundred fifty-one".