21138472 has 16 divisors (see below), whose sum is σ = 41358240. Its totient is φ = 10109616.

The previous prime is 21138451. The next prime is 21138473. The reversal of 21138472 is 27483112.

It is a self number, because there is not a number n which added to its sum of digits gives 21138472.

It is not an unprimeable number, because it can be changed into a prime (21138473) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 57258 + ... + 57625.

It is an arithmetic number, because the mean of its divisors is an integer number (2584890).

Almost surely, 2^21138472 is an apocalyptic number.

It is an amenable number.

21138472 is a deficient number, since it is larger than the sum of its proper divisors (20219768).

21138472 is a wasteful number, since it uses less digits than its factorization.

21138472 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 114912 (or 114908 counting only the distinct ones).

The product of its digits is 2688, while the sum is 28.

The square root of 21138472 is about 4597.6594045231. The cubic root of 21138472 is about 276.4974924208.

It can be divided in two parts, 2113 and 8472, that added together give a triangular number (10585 = T₁₄₅).

The spelling of 21138472 in words is "twenty-one million, one hundred thirty-eight thousand, four hundred seventy-two".