21473920 has 128 divisors (see below), whose sum is σ = 57834000. Its totient is φ = 7569408.

The previous prime is 21473909. The next prime is 21473923. The reversal of 21473920 is 2937412.

It can be written as a sum of positive squares in 8 ways, for example, as 2742336 + 18731584 = 1656^2 + 4328^2 .

It is a tau number, because it is divible by the number of its divisors (128).

It is a super-2 number, since 2×21473920² = 922258480332800, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21473923) 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, 241236 + ... + 241324.

Almost surely, 2^21473920 is an apocalyptic number.

21473920 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21473920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28917000).

21473920 is an abundant number, since it is smaller than the sum of its proper divisors (36360080).

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

21473920 is a wasteful number, since it uses less digits than its factorization.

21473920 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 150 (or 138 counting only the distinct ones).

The product of its (nonzero) digits is 3024, while the sum is 28.

The square root of 21473920 is about 4633.9961156652. The cubic root of 21473920 is about 277.9524097754.

The spelling of 21473920 in words is "twenty-one million, four hundred seventy-three thousand, nine hundred twenty".