21138936 has 64 divisors (see below), whose sum is σ = 65049600. Its totient is φ = 5574528.

The previous prime is 21138917. The next prime is 21138937. The reversal of 21138936 is 63983112.

It is a super-3 number, since 3×21138936³ (a number of 23 digits) contains 333 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21138897 and 21138906.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21138937) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 2656 + ... + 7023.

It is an arithmetic number, because the mean of its divisors is an integer number (1016400).

Almost surely, 2^21138936 is an apocalyptic number.

21138936 is a gapful number since it is divisible by the number (26) formed by its first and last digit.

It is an amenable number.

21138936 is an abundant number, since it is smaller than the sum of its proper divisors (43910664).

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

21138936 is a wasteful number, since it uses less digits than its factorization.

21138936 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9708 (or 9704 counting only the distinct ones).

The product of its digits is 7776, while the sum is 33.

The square root of 21138936 is about 4597.7098647044. The cubic root of 21138936 is about 276.4995154919.

The spelling of 21138936 in words is "twenty-one million, one hundred thirty-eight thousand, nine hundred thirty-six".