21520828 has 24 divisors (see below), whose sum is σ = 44207072. Its totient is φ = 8973504.

The previous prime is 21520799. The next prime is 21520831. The reversal of 21520828 is 82802512.

It is a Harshad number since it is a multiple of its sum of digits (28).

It is a junction number, because it is equal to n+sod(n) for n = 21520796 and 21520805.

It is a congruent number.

It is an unprimeable number.

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 7 ways as a sum of consecutive naturals, for example, 9351 + ... + 11422.

Almost surely, 2^21520828 is an apocalyptic number.

21520828 is a gapful number since it is divisible by the number (28) formed by its first and last digit.

It is an amenable number.

21520828 is an abundant number, since it is smaller than the sum of its proper divisors (22686244).

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

21520828 is a wasteful number, since it uses less digits than its factorization.

21520828 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 20821 (or 20819 counting only the distinct ones).

The product of its (nonzero) digits is 2560, while the sum is 28.

The square root of 21520828 is about 4639.0546450759. The cubic root of 21520828 is about 278.1546505947.

The spelling of 21520828 in words is "twenty-one million, five hundred twenty thousand, eight hundred twenty-eight".