39978913 has 4 divisors (see below), whose sum is σ = 43054228. Its totient is φ = 36903600.

The previous prime is 39978857. The next prime is 39978919. The reversal of 39978913 is 31987993.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 31987993 = 137 ⋅233489.

It can be written as a sum of positive squares in 2 ways, for example, as 23882769 + 16096144 = 4887^2 + 4012^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-39978913 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (39978919) 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, 1537638 + ... + 1537663.

It is an arithmetic number, because the mean of its divisors is an integer number (10763557).

Almost surely, 2^39978913 is an apocalyptic number.

It is an amenable number.

39978913 is a deficient number, since it is larger than the sum of its proper divisors (3075315).

39978913 is a wasteful number, since it uses less digits than its factorization.

39978913 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3075314.

The product of its digits is 367416, while the sum is 49.

The square root of 39978913 is about 6322.8880268434. Note that the first 3 decimals coincide. The cubic root of 39978913 is about 341.9350816670.

The spelling of 39978913 in words is "thirty-nine million, nine hundred seventy-eight thousand, nine hundred thirteen".