21521122065 has 40 divisors (see below), whose sum is σ = 40609071360. Its totient is φ = 10873826208.

The previous prime is 21521122061. The next prime is 21521122081. The reversal of 21521122065 is 56022112512.

It is not a de Polignac number, because 21521122065 - 2² = 21521122061 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is not an unprimeable number, because it can be changed into a prime (21521122061) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 39 ways as a sum of consecutive naturals, for example, 1390689 + ... + 1406078.

It is an arithmetic number, because the mean of its divisors is an integer number (1015226784).

Almost surely, 2^21521122065 is an apocalyptic number.

It is an amenable number.

21521122065 is a deficient number, since it is larger than the sum of its proper divisors (19087949295).

21521122065 is a wasteful number, since it uses less digits than its factorization.

21521122065 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2796803 (or 2796794 counting only the distinct ones).

The product of its (nonzero) digits is 2400, while the sum is 27.

Adding to 21521122065 its reverse (56022112512), we get a palindrome (77543234577).

The spelling of 21521122065 in words is "twenty-one billion, five hundred twenty-one million, one hundred twenty-two thousand, sixty-five".