21628520 has 16 divisors (see below), whose sum is σ = 48664260. Its totient is φ = 8651392.

The previous prime is 21628501. The next prime is 21628553. The reversal of 21628520 is 2582612.

It can be written as a sum of positive squares in 2 ways, for example, as 18852964 + 2775556 = 4342^2 + 1666^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 21628520.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 270317 + ... + 270396.

Almost surely, 2^21628520 is an apocalyptic number.

21628520 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21628520 is an abundant number, since it is smaller than the sum of its proper divisors (27035740).

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

21628520 is a wasteful number, since it uses less digits than its factorization.

21628520 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 540724 (or 540720 counting only the distinct ones).

The product of its (nonzero) digits is 1920, while the sum is 26.

The square root of 21628520 is about 4650.6472667791. The cubic root of 21628520 is about 278.6178484367.

The spelling of 21628520 in words is "twenty-one million, six hundred twenty-eight thousand, five hundred twenty".