21404520 has 64 divisors (see below), whose sum is σ = 71352000. Its totient is φ = 5707584.

The previous prime is 21404503. The next prime is 21404531. The reversal of 21404520 is 2540412.

21404520 is a `hidden beast` number, since 2 + 140 + 4 + 520 = 666.

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a junction number, because it is equal to n+sod(n) for n = 21404493 and 21404502.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 8830 + ... + 10989.

It is an arithmetic number, because the mean of its divisors is an integer number (1114875).

Almost surely, 2^21404520 is an apocalyptic number.

21404520 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21404520 is an abundant number, since it is smaller than the sum of its proper divisors (49947480).

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

21404520 is a wasteful number, since it uses less digits than its factorization.

21404520 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 19839 (or 19829 counting only the distinct ones).

The product of its (nonzero) digits is 320, while the sum is 18.

The square root of 21404520 is about 4626.5019182964. The cubic root of 21404520 is about 277.6526552333.

Adding to 21404520 its reverse (2540412), we get a palindrome (23944932).

The spelling of 21404520 in words is "twenty-one million, four hundred four thousand, five hundred twenty".