31689397 has 4 divisors (see below), whose sum is σ = 33357280. Its totient is φ = 30021516.

The previous prime is 31689379. The next prime is 31689403. The reversal of 31689397 is 79398613.

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, and also an emirpimes, since its reverse is a distinct semiprime: 79398613 = 7 ⋅11342659.

It is a cyclic number.

It is not a de Polignac number, because 31689397 - 2¹⁹ = 31165109 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 (31689337) 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, 833913 + ... + 833950.

It is an arithmetic number, because the mean of its divisors is an integer number (8339320).

Almost surely, 2^31689397 is an apocalyptic number.

It is an amenable number.

31689397 is a deficient number, since it is larger than the sum of its proper divisors (1667883).

31689397 is a wasteful number, since it uses less digits than its factorization.

31689397 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1667882.

The product of its digits is 244944, while the sum is 46.

The square root of 31689397 is about 5629.3336195326. Note that the first 3 decimals coincide. The cubic root of 31689397 is about 316.4496782483.

The spelling of 31689397 in words is "thirty-one million, six hundred eighty-nine thousand, three hundred ninety-seven".