21531432309 has 4 divisors (see below), whose sum is σ = 28708576416. Its totient is φ = 14354288204.

The previous prime is 21531432289. The next prime is 21531432319. The reversal of 21531432309 is 90323413512.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21531432309 - 2⁵ = 21531432277 is a prime.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 21531432309.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21531432319) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3588572049 + ... + 3588572054.

It is an arithmetic number, because the mean of its divisors is an integer number (7177144104).

Almost surely, 2^21531432309 is an apocalyptic number.

It is an amenable number.

21531432309 is a deficient number, since it is larger than the sum of its proper divisors (7177144107).

21531432309 is an equidigital number, since it uses as much as digits as its factorization.

21531432309 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7177144106.

The product of its (nonzero) digits is 19440, while the sum is 33.

The spelling of 21531432309 in words is "twenty-one billion, five hundred thirty-one million, four hundred thirty-two thousand, three hundred nine".