78391440 has 60 divisors (see below), whose sum is σ = 263267004. Its totient is φ = 20904192.

The previous prime is 78391421. The next prime is 78391447. The reversal of 78391440 is 4419387.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 52012944 + 26378496 = 7212^2 + 5136^2 .

It is a tau number, because it is divible by the number of its divisors (60).

It is a super-2 number, since 2×78391440² = 12290435730547200, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a junction number, because it is equal to n+sod(n) for n = 78391395 and 78391404.

It is not an unprimeable number, because it can be changed into a prime (78391447) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 53719 + ... + 55158.

Almost surely, 2^78391440 is an apocalyptic number.

It is an amenable number.

78391440 is an abundant number, since it is smaller than the sum of its proper divisors (184875564).

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

78391440 is a wasteful number, since it uses less digits than its factorization.

78391440 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 108896 (or 108887 counting only the distinct ones).

The product of its (nonzero) digits is 24192, while the sum is 36.

The square root of 78391440 is about 8853.8940585485. The cubic root of 78391440 is about 427.9794149706.

The spelling of 78391440 in words is "seventy-eight million, three hundred ninety-one thousand, four hundred forty".