21615206251501 has 16 divisors (see below), whose sum is σ = 22163138936496. Its totient is φ = 21072604074496.

The previous prime is 21615206251451. The next prime is 21615206251537. The reversal of 21615206251501 is 10515260251612.

It can be written as a sum of positive squares in 8 ways, for example, as 7784803095876 + 13830403155625 = 2790126^2 + 3718925^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21615206251501 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21615206252501) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 15209721 + ... + 16570033.

It is an arithmetic number, because the mean of its divisors is an integer number (1385196183531).

Almost surely, 2^{21615206251501} is an apocalyptic number.

It is an amenable number.

21615206251501 is a deficient number, since it is larger than the sum of its proper divisors (547932684995).

21615206251501 is a wasteful number, since it uses less digits than its factorization.

21615206251501 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1362272.

The product of its (nonzero) digits is 36000, while the sum is 37.

The spelling of 21615206251501 in words is "twenty-one trillion, six hundred fifteen billion, two hundred six million, two hundred fifty-one thousand, five hundred one".