81689680 has 40 divisors (see below), whose sum is σ = 194353632. Its totient is φ = 31914624.

The previous prime is 81689677. The next prime is 81689711. The reversal of 81689680 is 8698618.

81689680 = T₁₀₁ + T₁₀₂ + ... + T₇₈₈.

It is a tau number, because it is divible by the number of its divisors (40).

It is a self number, because there is not a number n which added to its sum of digits gives 81689680.

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, 8434 + ... + 15313.

Almost surely, 2^81689680 is an apocalyptic number.

81689680 is a gapful number since it is divisible by the number (80) formed by its first and last digit.

It is an amenable number.

81689680 is an abundant number, since it is smaller than the sum of its proper divisors (112663952).

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

81689680 is a wasteful number, since it uses less digits than its factorization.

81689680 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 23803 (or 23797 counting only the distinct ones).

The product of its (nonzero) digits is 165888, while the sum is 46.

The square root of 81689680 is about 9038.2343408433. The cubic root of 81689680 is about 433.8994153417.

It can be divided in two parts, 81689 and 680, that added together give a square (82369 = 287²).

The spelling of 81689680 in words is "eighty-one million, six hundred eighty-nine thousand, six hundred eighty".