21238255808 has 168 divisors, whose sum is σ = 54364426704. Its totient is φ = 8138188800.

The previous prime is 21238255789. The next prime is 21238255823. The reversal of 21238255808 is 80855283212.

It is a Harshad number since it is a multiple of its sum of digits (44).

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, 2099210 + ... + 2109302.

It is an arithmetic number, because the mean of its divisors is an integer number (323597778).

Almost surely, 2^21238255808 is an apocalyptic number.

21238255808 is a gapful number since it is divisible by the number (28) 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 21238255808, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (27182213352).

21238255808 is an abundant number, since it is smaller than the sum of its proper divisors (33126170896).

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

21238255808 is a wasteful number, since it uses less digits than its factorization.

21238255808 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10191 (or 10174 counting only the distinct ones).

The product of its (nonzero) digits is 307200, while the sum is 44.

The spelling of 21238255808 in words is "twenty-one billion, two hundred thirty-eight million, two hundred fifty-five thousand, eight hundred eight".