81686480 has 20 divisors (see below), whose sum is σ = 189921252. Its totient is φ = 32674560.

The previous prime is 81686459. The next prime is 81686531. The reversal of 81686480 is 8468618.

It can be written as a sum of positive squares in 2 ways, for example, as 8549776 + 73136704 = 2924^2 + 8552^2 .

It is a tau number, because it is divible by the number of its divisors (20).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 510461 + ... + 510620.

Almost surely, 2^81686480 is an apocalyptic number.

81686480 is a gapful number since it is divisible by the number (80) formed by its first and last digit.

It is an amenable number.

81686480 is an abundant number, since it is smaller than the sum of its proper divisors (108234772).

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

81686480 is a wasteful number, since it uses less digits than its factorization.

81686480 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1021094 (or 1021088 counting only the distinct ones).

The product of its (nonzero) digits is 73728, while the sum is 41.

The square root of 81686480 is about 9038.0573133832. The cubic root of 81686480 is about 433.8937496067.

The spelling of 81686480 in words is "eighty-one million, six hundred eighty-six thousand, four hundred eighty".