21420252 has 54 divisors (see below), whose sum is σ = 62990928. Its totient is φ = 6119568.

The previous prime is 21420251. The next prime is 21420257. The reversal of 21420252 is 25202412.

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21420251) by changing a digit.

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, 4308 + ... + 7835.

Almost surely, 2^21420252 is an apocalyptic number.

It is an amenable number.

21420252 is an abundant number, since it is smaller than the sum of its proper divisors (41570676).

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

21420252 is a wasteful number, since it uses less digits than its factorization.

21420252 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12167 (or 12155 counting only the distinct ones).

The product of its (nonzero) digits is 320, while the sum is 18.

The square root of 21420252 is about 4628.2018106388. The cubic root of 21420252 is about 277.7206620821.

Adding to 21420252 its reverse (25202412), we get a palindrome (46622664).

The spelling of 21420252 in words is "twenty-one million, four hundred twenty thousand, two hundred fifty-two".