21404720 has 40 divisors (see below), whose sum is σ = 51934176. Its totient is φ = 8188928.

The previous prime is 21404689. The next prime is 21404729. The reversal of 21404720 is 2740412.

It is a tau number, because it is divible by the number of its divisors (40).

It is a Harshad number since it is a multiple of its sum of digits (20).

It is a junction number, because it is equal to n+sod(n) for n = 21404692 and 21404701.

It is not an unprimeable number, because it can be changed into a prime (21404729) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 3977 + ... + 7656.

Almost surely, 2^21404720 is an apocalyptic number.

21404720 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21404720 is an abundant number, since it is smaller than the sum of its proper divisors (30529456).

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

21404720 is a wasteful number, since it uses less digits than its factorization.

21404720 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11669 (or 11663 counting only the distinct ones).

The product of its (nonzero) digits is 448, while the sum is 20.

The square root of 21404720 is about 4626.5235328484. The cubic root of 21404720 is about 277.6535200095.

The spelling of 21404720 in words is "twenty-one million, four hundred four thousand, seven hundred twenty".