31728609 has 24 divisors (see below), whose sum is σ = 50948352. Its totient is φ = 18863520.

The previous prime is 31728577. The next prime is 31728611. The reversal of 31728609 is 90682713.

It is not a de Polignac number, because 31728609 - 2⁵ = 31728577 is a prime.

It is not an unprimeable number, because it can be changed into a prime (31728649) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 2224 + ... + 8270.

It is an arithmetic number, because the mean of its divisors is an integer number (2122848).

Almost surely, 2^31728609 is an apocalyptic number.

It is an amenable number.

31728609 is a deficient number, since it is larger than the sum of its proper divisors (19219743).

31728609 is a wasteful number, since it uses less digits than its factorization.

31728609 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6117 (or 6114 counting only the distinct ones).

The product of its (nonzero) digits is 18144, while the sum is 36.

The square root of 31728609 is about 5632.8153706650. The cubic root of 31728609 is about 316.5801478626.

It can be divided in two parts, 3172 and 8609, that added together give a triangular number (11781 = T₁₅₃).

The spelling of 31728609 in words is "thirty-one million, seven hundred twenty-eight thousand, six hundred nine".