81785840 has 40 divisors (see below), whose sum is σ = 190956528. Its totient is φ = 32576000.

The previous prime is 81785839. The next prime is 81785863. The reversal of 81785840 is 4858718.

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

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, 18044 + ... + 22116.

Almost surely, 2^81785840 is an apocalyptic number.

81785840 is a gapful number since it is divisible by the number (80) formed by its first and last digit.

It is an amenable number.

81785840 is an abundant number, since it is smaller than the sum of its proper divisors (109170688).

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

81785840 is a wasteful number, since it uses less digits than its factorization.

81785840 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4337 (or 4331 counting only the distinct ones).

The product of its (nonzero) digits is 71680, while the sum is 41.

The square root of 81785840 is about 9043.5523993617. The cubic root of 81785840 is about 434.0696016980.

The spelling of 81785840 in words is "eighty-one million, seven hundred eighty-five thousand, eight hundred forty".