131721609 has 4 divisors (see below), whose sum is σ = 175628816. Its totient is φ = 87814404.

The previous prime is 131721563. The next prime is 131721613. The reversal of 131721609 is 906127131.

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 not a de Polignac number, because 131721609 - 2⁷ = 131721481 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (131721619) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 21953599 + ... + 21953604.

It is an arithmetic number, because the mean of its divisors is an integer number (43907204).

Almost surely, 2^131721609 is an apocalyptic number.

It is an amenable number.

131721609 is a deficient number, since it is larger than the sum of its proper divisors (43907207).

131721609 is an equidigital number, since it uses as much as digits as its factorization.

131721609 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 43907206.

The product of its (nonzero) digits is 2268, while the sum is 30.

The square root of 131721609 is about 11477.0034852308. The cubic root of 131721609 is about 508.8061386455.

The spelling of 131721609 in words is "one hundred thirty-one million, seven hundred twenty-one thousand, six hundred nine".