21815162221 has 8 divisors (see below), whose sum is σ = 21873737144. Its totient is φ = 21756625920.

The previous prime is 21815162197. The next prime is 21815162251. The reversal of 21815162221 is 12226151812.

It can be written as a sum of positive squares in 4 ways, for example, as 10110302500 + 11704859721 = 100550^2 + 108189^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21815162221 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 (21815162251) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1385131 + ... + 1400791.

It is an arithmetic number, because the mean of its divisors is an integer number (2734217143).

Almost surely, 2^21815162221 is an apocalyptic number.

It is an amenable number.

21815162221 is a deficient number, since it is larger than the sum of its proper divisors (58574923).

21815162221 is a wasteful number, since it uses less digits than its factorization.

21815162221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 19311.

The product of its digits is 3840, while the sum is 31.

The spelling of 21815162221 in words is "twenty-one billion, eight hundred fifteen million, one hundred sixty-two thousand, two hundred twenty-one".