21420204 has 96 divisors (see below), whose sum is σ = 58677696. Its totient is φ = 6021120.

The previous prime is 21420169. The next prime is 21420209. The reversal of 21420204 is 40202412.

It is not an unprimeable number, because it can be changed into a prime (21420209) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 108634 + ... + 108830.

It is an arithmetic number, because the mean of its divisors is an integer number (611226).

Almost surely, 2^21420204 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 21420204, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29338848).

21420204 is an abundant number, since it is smaller than the sum of its proper divisors (37257492).

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

21420204 is a wasteful number, since it uses less digits than its factorization.

21420204 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 275 (or 273 counting only the distinct ones).

The product of its (nonzero) digits is 128, while the sum is 15.

The square root of 21420204 is about 4628.1966250366. The cubic root of 21420204 is about 277.7204546366.

Adding to 21420204 its reverse (40202412), we get a palindrome (61622616).

The spelling of 21420204 in words is "twenty-one million, four hundred twenty thousand, two hundred four".