21023579556 has 108 divisors (see below), whose sum is σ = 61933215708. Its totient is φ = 5995672704.

The previous prime is 21023579543. The next prime is 21023579581. The reversal of 21023579556 is 65597532012.

21023579556 is a `hidden beast` number, since 2 + 1 + 0 + 23 + 5 + 79 + 556 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 12368998656 + 8654580900 = 111216^2 + 93030^2 .

It is a super-2 number, since 2×21023579556² (a number of 21 digits) contains 22 as substring.

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 35 ways as a sum of consecutive naturals, for example, 971850 + ... + 993246.

It is an arithmetic number, because the mean of its divisors is an integer number (573455701).

Almost surely, 2^21023579556 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21023579556, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (30966607854).

21023579556 is an abundant number, since it is smaller than the sum of its proper divisors (40909636152).

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

21023579556 is a wasteful number, since it uses less digits than its factorization.

21023579556 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 21978 (or 21966 counting only the distinct ones).

The product of its (nonzero) digits is 567000, while the sum is 45.

The spelling of 21023579556 in words is "twenty-one billion, twenty-three million, five hundred seventy-nine thousand, five hundred fifty-six".