21420936 has 56 divisors (see below), whose sum is σ = 60235230. Its totient is φ = 7138368.

The previous prime is 21420887. The next prime is 21420941. The reversal of 21420936 is 63902412.

It can be written as a sum of positive squares in only one way, i.e., 21068100 + 352836 = 4590^2 + 594^2 .

It is a Harshad number since it is a multiple of its sum of digits (27).

It is an unprimeable number.

It is a polite number, since it can be written in 13 ways as a sum of consecutive naturals, for example, 3996 + ... + 7668.

Almost surely, 2^21420936 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21420936, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (30117615).

21420936 is an abundant number, since it is smaller than the sum of its proper divisors (38814294).

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

21420936 is an equidigital number, since it uses as much as digits as its factorization.

21420936 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3697 (or 3678 counting only the distinct ones).

The product of its (nonzero) digits is 2592, while the sum is 27.

The square root of 21420936 is about 4628.2757048387. The cubic root of 21420936 is about 277.7236181461.

The spelling of 21420936 in words is "twenty-one million, four hundred twenty thousand, nine hundred thirty-six".