39987917 has 4 divisors (see below), whose sum is σ = 40742460. Its totient is φ = 39233376.

The previous prime is 39987907. The next prime is 39987919. The reversal of 39987917 is 71978993.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 14394436 + 25593481 = 3794^2 + 5059^2 .

It is a cyclic number.

It is not a de Polignac number, because 39987917 - 2⁴ = 39987901 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (53), and also a Moran number because the ratio is a prime number: 754489 = 39987917 / (3 + 9 + 9 + 8 + 7 + 9 + 1 + 7).

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (39987919) 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, 377192 + ... + 377297.

It is an arithmetic number, because the mean of its divisors is an integer number (10185615).

Almost surely, 2^39987917 is an apocalyptic number.

It is an amenable number.

39987917 is a deficient number, since it is larger than the sum of its proper divisors (754543).

39987917 is an equidigital number, since it uses as much as digits as its factorization.

39987917 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 754542.

The product of its digits is 857304, while the sum is 53.

The square root of 39987917 is about 6323.6000031628. The cubic root of 39987917 is about 341.9607498017.

It can be divided in two parts, 39987 and 917, that added together give a palindrome (40904).

The spelling of 39987917 in words is "thirty-nine million, nine hundred eighty-seven thousand, nine hundred seventeen".