21039220 has 12 divisors (see below), whose sum is σ = 44182404. Its totient is φ = 8415680.

The previous prime is 21039197. The next prime is 21039229. The reversal of 21039220 is 2293012.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 5262436 + 15776784 = 2294^2 + 3972^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21039229) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 525961 + ... + 526000.

It is an arithmetic number, because the mean of its divisors is an integer number (3681867).

Almost surely, 2^21039220 is an apocalyptic number.

21039220 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21039220 is an abundant number, since it is smaller than the sum of its proper divisors (23143184).

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

21039220 is a wasteful number, since it uses less digits than its factorization.

21039220 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1051970 (or 1051968 counting only the distinct ones).

The product of its (nonzero) digits is 216, while the sum is 19.

The square root of 21039220 is about 4586.8529516434. The cubic root of 21039220 is about 276.0640648033.

The spelling of 21039220 in words is "twenty-one million, thirty-nine thousand, two hundred twenty".