39991639 has 4 divisors (see below), whose sum is σ = 40134240. Its totient is φ = 39849040.

The previous prime is 39991619. The next prime is 39991669. The reversal of 39991639 is 93619993.

It is a happy number.

39991639 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 93619993 = 9521 ⋅9833.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-39991639 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 39991592 and 39991601.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (39991619) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 70879 + ... + 71440.

It is an arithmetic number, because the mean of its divisors is an integer number (10033560).

Almost surely, 2^39991639 is an apocalyptic number.

39991639 is a deficient number, since it is larger than the sum of its proper divisors (142601).

39991639 is a wasteful number, since it uses less digits than its factorization.

39991639 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 142600.

The product of its digits is 354294, while the sum is 49.

The square root of 39991639 is about 6323.8942907041. The cubic root of 39991639 is about 341.9713591601.

The spelling of 39991639 in words is "thirty-nine million, nine hundred ninety-one thousand, six hundred thirty-nine".