21520515411551 has 6 divisors (see below), whose sum is σ = 23303280002040. Its totient is φ = 19865091148968.

The previous prime is 21520515411497. The next prime is 21520515411569. The reversal of 21520515411551 is 15511451502512.

It is not a de Polignac number, because 21520515411551 - 2⁶ = 21520515411487 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 (21520515411851) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 63670163771 + ... + 63670164108.

It is an arithmetic number, because the mean of its divisors is an integer number (3883880000340).

Almost surely, 2^{21520515411551} is an apocalyptic number.

21520515411551 is a deficient number, since it is larger than the sum of its proper divisors (1782764590489).

21520515411551 is a wasteful number, since it uses less digits than its factorization.

21520515411551 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 127340327905 (or 127340327892 counting only the distinct ones).

The product of its (nonzero) digits is 50000, while the sum is 38.

The spelling of 21520515411551 in words is "twenty-one trillion, five hundred twenty billion, five hundred fifteen million, four hundred eleven thousand, five hundred fifty-one".