39991999 has 4 divisors (see below), whose sum is σ = 40365864. Its totient is φ = 39618136.

The previous prime is 39991997. The next prime is 39992003. The reversal of 39991999 is 99919993.

It is a happy number.

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

It is a cyclic number.

It is not a de Polignac number, because 39991999 - 2¹ = 39991997 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 (39991993) 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, 186772 + ... + 186985.

It is an arithmetic number, because the mean of its divisors is an integer number (10091466).

Almost surely, 2^39991999 is an apocalyptic number.

39991999 is a deficient number, since it is larger than the sum of its proper divisors (373865).

39991999 is a wasteful number, since it uses less digits than its factorization.

39991999 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 373864.

The product of its digits is 1594323, while the sum is 58.

The square root of 39991999 is about 6323.9227541139. The cubic root of 39991999 is about 341.9723852856.

It can be divided in two parts, 3999 and 1999, that multiplied together give a triangular number (7994001 = T₃₉₉₈).

The spelling of 39991999 in words is "thirty-nine million, nine hundred ninety-one thousand, nine hundred ninety-nine".