81859440 has 80 divisors (see below), whose sum is σ = 273295008. Its totient is φ = 20149248.

The previous prime is 81859439. The next prime is 81859457. The reversal of 81859440 is 4495818.

It is a tau number, because it is divible by the number of its divisors (80).

It is a super-2 number, since 2×81859440² = 13401935834227200, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (39).

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 9999 + ... + 16238.

Almost surely, 2^81859440 is an apocalyptic number.

81859440 is a gapful number since it is divisible by the number (80) formed by its first and last digit.

It is an amenable number.

81859440 is an abundant number, since it is smaller than the sum of its proper divisors (191435568).

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

81859440 is a wasteful number, since it uses less digits than its factorization.

81859440 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 26266 (or 26260 counting only the distinct ones).

The product of its (nonzero) digits is 46080, while the sum is 39.

The square root of 81859440 is about 9047.6206817041. The cubic root of 81859440 is about 434.1997707026.

The spelling of 81859440 in words is "eighty-one million, eight hundred fifty-nine thousand, four hundred forty".