81720378 has 24 divisors (see below), whose sum is σ = 177393216. Its totient is φ = 27189000.

The previous prime is 81720313. The next prime is 81720409. The reversal of 81720378 is 87302718.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 6303 + ... + 14253.

It is an arithmetic number, because the mean of its divisors is an integer number (7391384).

Almost surely, 2^81720378 is an apocalyptic number.

81720378 is an abundant number, since it is smaller than the sum of its proper divisors (95672838).

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

81720378 is a wasteful number, since it uses less digits than its factorization.

81720378 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8530 (or 8527 counting only the distinct ones).

The product of its (nonzero) digits is 18816, while the sum is 36.

The square root of 81720378 is about 9039.9324112518. The cubic root of 81720378 is about 433.9537599302.

It can be divided in two parts, 817203 and 78, that added together give a triangular number (817281 = T₁₂₇₈).

The spelling of 81720378 in words is "eighty-one million, seven hundred twenty thousand, three hundred seventy-eight".