21312420 has 48 divisors (see below), whose sum is σ = 59875200. Its totient is φ = 5664256.

The previous prime is 21312341. The next prime is 21312427. The reversal of 21312420 is 2421312.

It is a Harshad number since it is a multiple of its sum of digits (15).

It is a self number, because there is not a number n which added to its sum of digits gives 21312420.

It is not an unprimeable number, because it can be changed into a prime (21312427) 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, 35281 + ... + 35879.

It is an arithmetic number, because the mean of its divisors is an integer number (1247400).

Almost surely, 2^21312420 is an apocalyptic number.

21312420 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21312420 is an abundant number, since it is smaller than the sum of its proper divisors (38562780).

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

21312420 is a wasteful number, since it uses less digits than its factorization.

21312420 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1204 (or 1202 counting only the distinct ones).

The product of its (nonzero) digits is 96, while the sum is 15.

The square root of 21312420 is about 4616.5376636609. The cubic root of 21312420 is about 277.2538520129.

Adding to 21312420 its reverse (2421312), we get a palindrome (23733732).

The spelling of 21312420 in words is "twenty-one million, three hundred twelve thousand, four hundred twenty".