31981647 has 4 divisors (see below), whose sum is σ = 42642200. Its totient is φ = 21321096.

The previous prime is 31981639. The next prime is 31981711. The reversal of 31981647 is 74618913.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 74618913 = 3 ⋅24872971.

It is not a de Polignac number, because 31981647 - 2³ = 31981639 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (31981627) 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, 5330272 + ... + 5330277.

It is an arithmetic number, because the mean of its divisors is an integer number (10660550).

Almost surely, 2^31981647 is an apocalyptic number.

31981647 is a deficient number, since it is larger than the sum of its proper divisors (10660553).

31981647 is a wasteful number, since it uses less digits than its factorization.

31981647 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10660552.

The product of its digits is 36288, while the sum is 39.

The square root of 31981647 is about 5655.2318254869. The cubic root of 31981647 is about 317.4195038458.

The spelling of 31981647 in words is "thirty-one million, nine hundred eighty-one thousand, six hundred forty-seven".