21138456 has 32 divisors (see below), whose sum is σ = 54077760. Its totient is φ = 6881952.

The previous prime is 21138451. The next prime is 21138473. The reversal of 21138456 is 65483112.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21138451) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 9210 + ... + 11273.

It is an arithmetic number, because the mean of its divisors is an integer number (1689930).

Almost surely, 2^21138456 is an apocalyptic number.

It is an amenable number.

21138456 is an abundant number, since it is smaller than the sum of its proper divisors (32939304).

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

21138456 is a wasteful number, since it uses less digits than its factorization.

21138456 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 20535 (or 20531 counting only the distinct ones).

The product of its digits is 5760, while the sum is 30.

The square root of 21138456 is about 4597.6576645070. The cubic root of 21138456 is about 276.4974226592.

The spelling of 21138456 in words is "twenty-one million, one hundred thirty-eight thousand, four hundred fifty-six".