21255655212 has 108 divisors (see below), whose sum is σ = 61094975760. Its totient is φ = 6218963520.

The previous prime is 21255655193. The next prime is 21255655231.

21255655212 is a `hidden beast` number, since 2 + 125 + 5 + 6 + 5 + 521 + 2 = 666.

21255655212 is nontrivially palindromic in base 10.

It is an interprime number because it is at equal distance from previous prime (21255655193) and next prime (21255655231).

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 35 ways as a sum of consecutive naturals, for example, 42193 + ... + 210455.

It is an arithmetic number, because the mean of its divisors is an integer number (565694220).

Almost surely, 2^21255655212 is an apocalyptic number.

21255655212 is a gapful number since it is divisible by the number (22) 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 21255655212, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (30547487880).

21255655212 is an abundant number, since it is smaller than the sum of its proper divisors (39839320548).

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

21255655212 is a wasteful number, since it uses less digits than its factorization.

21255655212 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 168324 (or 168308 counting only the distinct ones).

The product of its digits is 60000, while the sum is 36.

The spelling of 21255655212 in words is "twenty-one billion, two hundred fifty-five million, six hundred fifty-five thousand, two hundred twelve".