21504660881 has 4 divisors (see below), whose sum is σ = 23459630064. Its totient is φ = 19549691700.

The previous prime is 21504660869. The next prime is 21504660889. The reversal of 21504660881 is 18806640512.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 21504660881 - 2¹⁸ = 21504398737 is a prime.

It is a super-2 number, since 2×21504660881² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21504660889) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 977484575 + ... + 977484596.

It is an arithmetic number, because the mean of its divisors is an integer number (5864907516).

Almost surely, 2^21504660881 is an apocalyptic number.

It is an amenable number.

21504660881 is a deficient number, since it is larger than the sum of its proper divisors (1954969183).

21504660881 is a wasteful number, since it uses less digits than its factorization.

21504660881 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1954969182.

The product of its (nonzero) digits is 92160, while the sum is 41.

The spelling of 21504660881 in words is "twenty-one billion, five hundred four million, six hundred sixty thousand, eight hundred eighty-one".