21528770 has 16 divisors (see below), whose sum is σ = 38822328. Its totient is φ = 8595840.

The previous prime is 21528769. The next prime is 21528779. The reversal of 21528770 is 7782512.

It can be written as a sum of positive squares in 4 ways, for example, as 21279769 + 249001 = 4613^2 + 499^2 .

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

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 4982 + ... + 8238.

Almost surely, 2^21528770 is an apocalyptic number.

21528770 is a deficient number, since it is larger than the sum of its proper divisors (17293558).

21528770 is a wasteful number, since it uses less digits than its factorization.

21528770 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3925.

The product of its (nonzero) digits is 7840, while the sum is 32.

The square root of 21528770 is about 4639.9105594828. The cubic root of 21528770 is about 278.1888629175.

The spelling of 21528770 in words is "twenty-one million, five hundred twenty-eight thousand, seven hundred seventy".