39999921 has 32 divisors (see below), whose sum is σ = 63114240. Its totient is φ = 22296384.

The previous prime is 39999919. The next prime is 39999931. The reversal of 39999921 is 12999993.

It is not a de Polignac number, because 39999921 - 2¹ = 39999919 is a prime.

It is not an unprimeable number, because it can be changed into a prime (39999901) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 15870 + ... + 18216.

It is an arithmetic number, because the mean of its divisors is an integer number (1972320).

Almost surely, 2^39999921 is an apocalyptic number.

It is an amenable number.

39999921 is a deficient number, since it is larger than the sum of its proper divisors (23114319).

39999921 is a wasteful number, since it uses less digits than its factorization.

39999921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2405.

The product of its digits is 354294, while the sum is 51.

The square root of 39999921 is about 6324.5490748353. The cubic root of 39999921 is about 341.9949641884.

It can be divided in two parts, 3999992 and 1, that added together give a palindrome (3999993).

The spelling of 39999921 in words is "thirty-nine million, nine hundred ninety-nine thousand, nine hundred twenty-one".