13921978 has 12 divisors (see below), whose sum is σ = 24292602. Its totient is φ = 5966520.

The previous prime is 13921961. The next prime is 13921979. The reversal of 13921978 is 87912931.

It can be written as a sum of positive squares in only one way, i.e., 10323369 + 3598609 = 3213^2 + 1897^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 13921978.

It is not an unprimeable number, because it can be changed into a prime (13921979) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 70933 + ... + 71128.

Almost surely, 2^13921978 is an apocalyptic number.

13921978 is a deficient number, since it is larger than the sum of its proper divisors (10370624).

13921978 is a wasteful number, since it uses less digits than its factorization.

13921978 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 142077 (or 142070 counting only the distinct ones).

The product of its digits is 27216, while the sum is 40.

The square root of 13921978 is about 3731.2166916436. The cubic root of 13921978 is about 240.5656680161.

The spelling of 13921978 in words is "thirteen million, nine hundred twenty-one thousand, nine hundred seventy-eight".