81709278 has 32 divisors (see below), whose sum is σ = 187401984. Its totient is φ = 23265792.

The previous prime is 81709249. The next prime is 81709289. The reversal of 81709278 is 87290718.

It is a super-2 number, since 2×81709278² = 13352812222562568, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (42).

It is a plaindrome in base 12.

It is a congruent number.

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, 9726 + ... + 16062.

It is an arithmetic number, because the mean of its divisors is an integer number (5856312).

Almost surely, 2^81709278 is an apocalyptic number.

81709278 is an abundant number, since it is smaller than the sum of its proper divisors (105692706).

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

81709278 is a wasteful number, since it uses less digits than its factorization.

81709278 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6656.

The product of its (nonzero) digits is 56448, while the sum is 42.

The square root of 81709278 is about 9039.3184477592. The cubic root of 81709278 is about 433.9341112005.

The spelling of 81709278 in words is "eighty-one million, seven hundred nine thousand, two hundred seventy-eight".