21532809 has 16 divisors (see below), whose sum is σ = 29804544. Its totient is φ = 13818000.

The previous prime is 21532801. The next prime is 21532811. The reversal of 21532809 is 90823512.

It is a happy number.

It is not a de Polignac number, because 21532809 - 2³ = 21532801 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21532801) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 7984 + ... + 10334.

It is an arithmetic number, because the mean of its divisors is an integer number (1862784).

Almost surely, 2^21532809 is an apocalyptic number.

It is an amenable number.

21532809 is a deficient number, since it is larger than the sum of its proper divisors (8271735).

21532809 is a wasteful number, since it uses less digits than its factorization.

21532809 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2468.

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

The square root of 21532809 is about 4640.3457845294. The cubic root of 21532809 is about 278.2062587799.

The spelling of 21532809 in words is "twenty-one million, five hundred thirty-two thousand, eight hundred nine".