21420900 has 54 divisors (see below), whose sum is σ = 67145442. Its totient is φ = 5712000.

The previous prime is 21420887. The next prime is 21420941. The reversal of 21420900 is 902412.

It can be written as a sum of positive squares in 3 ways, for example, as 2965284 + 18455616 = 1722^2 + 4296^2 .

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

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 17 ways as a sum of consecutive naturals, for example, 11001 + ... + 12800.

Almost surely, 2^21420900 is an apocalyptic number.

21420900 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21420900 is an abundant number, since it is smaller than the sum of its proper divisors (45724542).

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

21420900 is a wasteful number, since it uses less digits than its factorization.

21420900 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 23821 (or 23811 counting only the distinct ones).

The product of its (nonzero) digits is 144, while the sum is 18.

The square root of 21420900 is about 4628.2718156997. The cubic root of 21420900 is about 277.7234625654.

The spelling of 21420900 in words is "twenty-one million, four hundred twenty thousand, nine hundred".