21855117420 has 72 divisors (see below), whose sum is σ = 66305991024. Its totient is φ = 5826964608.

The previous prime is 21855117419. The next prime is 21855117469. The reversal of 21855117420 is 2471155812.

It is a happy number.

21855117420 is a `hidden beast` number, since 2 + 18 + 551 + 1 + 74 + 20 = 666.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 1735587 + ... + 1748133.

It is an arithmetic number, because the mean of its divisors is an integer number (920916542).

Almost surely, 2^21855117420 is an apocalyptic number.

21855117420 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21855117420 is an abundant number, since it is smaller than the sum of its proper divisors (44450873604).

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

21855117420 is a wasteful number, since it uses less digits than its factorization.

21855117420 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 22239 (or 22234 counting only the distinct ones).

The product of its (nonzero) digits is 22400, while the sum is 36.

The spelling of 21855117420 in words is "twenty-one billion, eight hundred fifty-five million, one hundred seventeen thousand, four hundred twenty".