81378840 has 32 divisors (see below), whose sum is σ = 244136880. Its totient is φ = 21700992.

The previous prime is 81378839. The next prime is 81378859. The reversal of 81378840 is 4887318.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 338959 + ... + 339198.

Almost surely, 2^81378840 is an apocalyptic number.

It is an amenable number.

81378840 is an abundant number, since it is smaller than the sum of its proper divisors (162758040).

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

81378840 is a wasteful number, since it uses less digits than its factorization.

81378840 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 678171 (or 678167 counting only the distinct ones).

The product of its (nonzero) digits is 43008, while the sum is 39.

The square root of 81378840 is about 9021.0221150377. The cubic root of 81378840 is about 433.3483676572.

The spelling of 81378840 in words is "eighty-one million, three hundred seventy-eight thousand, eight hundred forty".