21528775 has 12 divisors (see below), whose sum is σ = 27096232. Its totient is φ = 16964640.

The previous prime is 21528769. The next prime is 21528779. The reversal of 21528775 is 57782512.

It is not a de Polignac number, because 21528775 - 2⁵ = 21528743 is a prime.

It is a hoax number, since the sum of its digits (37) coincides with the sum of the digits of its distinct prime factors.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21528779) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 4752 + ... + 8101.

Almost surely, 2^21528775 is an apocalyptic number.

21528775 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

21528775 is a deficient number, since it is larger than the sum of its proper divisors (5567457).

21528775 is a wasteful number, since it uses less digits than its factorization.

21528775 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12930 (or 12925 counting only the distinct ones).

The product of its digits is 39200, while the sum is 37.

The square root of 21528775 is about 4639.9110982863. The cubic root of 21528775 is about 278.1888844537.

The spelling of 21528775 in words is "twenty-one million, five hundred twenty-eight thousand, seven hundred seventy-five".