21361537221 has 16 divisors (see below), whose sum is σ = 30166354368. Its totient is φ = 13399366400.

The previous prime is 21361537193. The next prime is 21361537231. The reversal of 21361537221 is 12273516312.

It is a cyclic number.

It is not a de Polignac number, because 21361537221 - 2⁶ = 21361537157 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21361537231) 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 15 ways as a sum of consecutive naturals, for example, 118051 + ... + 238031.

It is an arithmetic number, because the mean of its divisors is an integer number (1885397148).

Almost surely, 2^21361537221 is an apocalyptic number.

It is an amenable number.

21361537221 is a deficient number, since it is larger than the sum of its proper divisors (8804817147).

21361537221 is a wasteful number, since it uses less digits than its factorization.

21361537221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 123492.

The product of its digits is 15120, while the sum is 33.

The spelling of 21361537221 in words is "twenty-one billion, three hundred sixty-one million, five hundred thirty-seven thousand, two hundred twenty-one".