71978640 has 80 divisors (see below), whose sum is σ = 223967808. Its totient is φ = 19122688.

The previous prime is 71978639. The next prime is 71978659. The reversal of 71978640 is 4687917.

It is a tau number, because it is divible by the number of its divisors (80).

It is a junction number, because it is equal to n+sod(n) for n = 71978592 and 71978601.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 105982 + ... + 106658.

Almost surely, 2^71978640 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 71978640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (111983904).

71978640 is an abundant number, since it is smaller than the sum of its proper divisors (151989168).

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

71978640 is a wasteful number, since it uses less digits than its factorization.

71978640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1136 (or 1130 counting only the distinct ones).

The product of its (nonzero) digits is 84672, while the sum is 42.

The square root of 71978640 is about 8484.0226308043. The cubic root of 71978640 is about 415.9756211059.

The spelling of 71978640 in words is "seventy-one million, nine hundred seventy-eight thousand, six hundred forty".