21255527521 has 4 divisors (see below), whose sum is σ = 21256641072. Its totient is φ = 21254413972.

The previous prime is 21255527509. The next prime is 21255527537. The reversal of 21255527521 is 12572555212.

It is a happy number.

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 a cyclic number.

It is not a de Polignac number, because 21255527521 - 2³¹ = 19108043873 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21255522521) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 527635 + ... + 566488.

It is an arithmetic number, because the mean of its divisors is an integer number (5314160268).

Almost surely, 2^21255527521 is an apocalyptic number.

It is an amenable number.

21255527521 is a deficient number, since it is larger than the sum of its proper divisors (1113551).

21255527521 is a wasteful number, since it uses less digits than its factorization.

21255527521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1113550.

The product of its digits is 70000, while the sum is 37.

The spelling of 21255527521 in words is "twenty-one billion, two hundred fifty-five million, five hundred twenty-seven thousand, five hundred twenty-one".