21456420 has 48 divisors (see below), whose sum is σ = 60341568. Its totient is φ = 5696640.

The previous prime is 21456419. The next prime is 21456427. The reversal of 21456420 is 2465412.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21456427) 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 15 ways as a sum of consecutive naturals, for example, 15975 + ... + 17265.

It is an arithmetic number, because the mean of its divisors is an integer number (1257116).

Almost surely, 2^21456420 is an apocalyptic number.

21456420 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21456420 is an abundant number, since it is smaller than the sum of its proper divisors (38885148).

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

21456420 is a wasteful number, since it uses less digits than its factorization.

21456420 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1580 (or 1578 counting only the distinct ones).

The product of its (nonzero) digits is 1920, while the sum is 24.

The square root of 21456420 is about 4632.1075117057. The cubic root of 21456420 is about 277.8768842215.

The spelling of 21456420 in words is "twenty-one million, four hundred fifty-six thousand, four hundred twenty".