21433509 has 12 divisors (see below), whose sum is σ = 31467852. Its totient is φ = 14054400.

The previous prime is 21433507. The next prime is 21433519. The reversal of 21433509 is 90533412.

It can be written as a sum of positive squares in 2 ways, for example, as 9941409 + 11492100 = 3153^2 + 3390^2 .

It is not a de Polignac number, because 21433509 - 2¹ = 21433507 is a prime.

It is a hoax number, since the sum of its digits (27) coincides with the sum of the digits of its distinct prime factors.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21433507) by changing a digit.

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 11 ways as a sum of consecutive naturals, for example, 18972 + ... + 20069.

It is an arithmetic number, because the mean of its divisors is an integer number (2622321).

Almost surely, 2^21433509 is an apocalyptic number.

It is an amenable number.

21433509 is a deficient number, since it is larger than the sum of its proper divisors (10034343).

21433509 is a wasteful number, since it uses less digits than its factorization.

21433509 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 39108 (or 39105 counting only the distinct ones).

The product of its (nonzero) digits is 3240, while the sum is 27.

The square root of 21433509 is about 4629.6337868129. The cubic root of 21433509 is about 277.7779440651. Note that the first 3 decimals are identical.

The spelling of 21433509 in words is "twenty-one million, four hundred thirty-three thousand, five hundred nine".