13978640 has 40 divisors (see below), whose sum is σ = 35002968. Its totient is φ = 5160960.

The previous prime is 13978639. The next prime is 13978649. The reversal of 13978640 is 4687931.

It can be written as a sum of positive squares in 4 ways, for example, as 80656 + 13897984 = 284^2 + 3728^2 .

It is a tau number, because it is divible by the number of its divisors (40).

It is a junction number, because it is equal to n+sod(n) for n = 13978594 and 13978603.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (13978649) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 5681 + ... + 7760.

Almost surely, 2^13978640 is an apocalyptic number.

13978640 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

13978640 is an abundant number, since it is smaller than the sum of its proper divisors (21024328).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

13978640 is a wasteful number, since it uses less digits than its factorization.

13978640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 13467 (or 13461 counting only the distinct ones).

The product of its (nonzero) digits is 36288, while the sum is 38.

The square root of 13978640 is about 3738.8019471483. The cubic root of 13978640 is about 240.8915910781.

The spelling of 13978640 in words is "thirteen million, nine hundred seventy-eight thousand, six hundred forty".