21138295920 has 160 divisors (see below), whose sum is σ = 74980581888. Its totient is φ = 4825764864.

The previous prime is 21138295883. The next prime is 21138295921. The reversal of 21138295920 is 2959283112.

It is a Harshad number since it is a multiple of its sum of digits (42).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21138295921) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 1466187 + ... + 1480533.

Almost surely, 2^21138295920 is an apocalyptic number.

21138295920 is a gapful number since it is divisible by the number (20) 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 21138295920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (37490290944).

21138295920 is an abundant number, since it is smaller than the sum of its proper divisors (53842285968).

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

21138295920 is a wasteful number, since it uses less digits than its factorization.

21138295920 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 15247 (or 15241 counting only the distinct ones).

The product of its (nonzero) digits is 77760, while the sum is 42.

The spelling of 21138295920 in words is "twenty-one billion, one hundred thirty-eight million, two hundred ninety-five thousand, nine hundred twenty".