21520389 has 16 divisors (see below), whose sum is σ = 31380480. Its totient is φ = 13010160.

The previous prime is 21520363. The next prime is 21520391. The reversal of 21520389 is 98302512.

It is a happy number.

It is not a de Polignac number, because 21520389 - 2⁸ = 21520133 is a prime.

It is a super-2 number, since 2×21520389² = 926254285422642, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21520399) 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 15 ways as a sum of consecutive naturals, for example, 23274 + ... + 24180.

It is an arithmetic number, because the mean of its divisors is an integer number (1961280).

Almost surely, 2^21520389 is an apocalyptic number.

It is an amenable number.

21520389 is a deficient number, since it is larger than the sum of its proper divisors (9860091).

21520389 is a wasteful number, since it uses less digits than its factorization.

21520389 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1640.

The product of its (nonzero) digits is 4320, while the sum is 30.

The square root of 21520389 is about 4639.0073291600. The cubic root of 21520389 is about 278.1527592375.

The spelling of 21520389 in words is "twenty-one million, five hundred twenty thousand, three hundred eighty-nine".