21399472 has 20 divisors (see below), whose sum is σ = 43644280. Its totient is φ = 10136448.

The previous prime is 21399457. The next prime is 21399473. The reversal of 21399472 is 27499312.

It is not an unprimeable number, because it can be changed into a prime (21399473) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 34893 + ... + 35500.

It is an arithmetic number, because the mean of its divisors is an integer number (2182214).

Almost surely, 2^21399472 is an apocalyptic number.

It is an amenable number.

21399472 is an abundant number, since it is smaller than the sum of its proper divisors (22244808).

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

21399472 is a wasteful number, since it uses less digits than its factorization.

21399472 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 70420 (or 70414 counting only the distinct ones).

The product of its digits is 27216, while the sum is 37.

The square root of 21399472 is about 4625.9563335596. The cubic root of 21399472 is about 277.6308264981.

It can be divided in two parts, 2139 and 9472, that added together give a palindrome (11611).

The spelling of 21399472 in words is "twenty-one million, three hundred ninety-nine thousand, four hundred seventy-two".