21311755556 has 96 divisors (see below), whose sum is σ = 47155530240. Its totient is φ = 8202009600.

The previous prime is 21311755547. The next prime is 21311755559. The reversal of 21311755556 is 65555711312.

It is a Harshad number since it is a multiple of its sum of digits (41).

It is not an unprimeable number, because it can be changed into a prime (21311755559) 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 31 ways as a sum of consecutive naturals, for example, 5803601 + ... + 5807271.

It is an arithmetic number, because the mean of its divisors is an integer number (491203440).

Almost surely, 2^21311755556 is an apocalyptic number.

21311755556 is a gapful number since it is divisible by the number (26) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21311755556, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (23577765120).

21311755556 is an abundant number, since it is smaller than the sum of its proper divisors (25843774684).

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

21311755556 is a wasteful number, since it uses less digits than its factorization.

21311755556 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4125 (or 4123 counting only the distinct ones).

The product of its digits is 157500, while the sum is 41.

The spelling of 21311755556 in words is "twenty-one billion, three hundred eleven million, seven hundred fifty-five thousand, five hundred fifty-six".