21259220 has 18 divisors (see below), whose sum is σ = 44687706. Its totient is φ = 8495440.

The previous prime is 21259219. The next prime is 21259223. The reversal of 21259220 is 2295212.

It can be written as a sum of positive squares in only one way, i.e., 17007376 + 4251844 = 4124^2 + 2062^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21259223) 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 5 ways as a sum of consecutive naturals, for example, 20105 + ... + 21135.

Almost surely, 2^21259220 is an apocalyptic number.

21259220 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21259220 is an abundant number, since it is smaller than the sum of its proper divisors (23428486).

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

21259220 is an equidigital number, since it uses as much as digits as its factorization.

21259220 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2071 (or 1038 counting only the distinct ones).

The product of its (nonzero) digits is 720, while the sum is 23.

The square root of 21259220 is about 4610.7721696046. The cubic root of 21259220 is about 277.0229663781.

Multiplying 21259220 by its product of nonzero digits (720), we get a square (15306638400 = 123720²).

The spelling of 21259220 in words is "twenty-one million, two hundred fifty-nine thousand, two hundred twenty".