21557122420 has 12 divisors (see below), whose sum is σ = 45269957124. Its totient is φ = 8622848960.

The previous prime is 21557122417. The next prime is 21557122469. The reversal of 21557122420 is 2422175512.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 3346159716 + 18210962704 = 57846^2 + 134948^2 .

It is a congruent number.

It is an unprimeable number.

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 3 ways as a sum of consecutive naturals, for example, 538928041 + ... + 538928080.

It is an arithmetic number, because the mean of its divisors is an integer number (3772496427).

Almost surely, 2^21557122420 is an apocalyptic number.

21557122420 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21557122420 is an abundant number, since it is smaller than the sum of its proper divisors (23712834704).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21557122420 is a wasteful number, since it uses less digits than its factorization.

21557122420 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1077856130 (or 1077856128 counting only the distinct ones).

The product of its (nonzero) digits is 11200, while the sum is 31.

Adding to 21557122420 its reverse (2422175512), we get a palindrome (23979297932).

The spelling of 21557122420 in words is "twenty-one billion, five hundred fifty-seven million, one hundred twenty-two thousand, four hundred twenty".