21138845 has 24 divisors (see below), whose sum is σ = 31782744. Its totient is φ = 13378176.

The previous prime is 21138823. The next prime is 21138847. The reversal of 21138845 is 54883112.

It can be written as a sum of positive squares in 4 ways, for example, as 879844 + 20259001 = 938^2 + 4501^2 .

It is not a de Polignac number, because 21138845 - 2⁶ = 21138781 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21138847) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 134 + ... + 6503.

It is an arithmetic number, because the mean of its divisors is an integer number (1324281).

Almost surely, 2^21138845 is an apocalyptic number.

It is an amenable number.

21138845 is a deficient number, since it is larger than the sum of its proper divisors (10643899).

21138845 is a wasteful number, since it uses less digits than its factorization.

21138845 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6669 (or 6662 counting only the distinct ones).

The product of its digits is 7680, while the sum is 32.

The square root of 21138845 is about 4597.6999684625. The cubic root of 21138845 is about 276.4991187282.

The spelling of 21138845 in words is "twenty-one million, one hundred thirty-eight thousand, eight hundred forty-five".