81774640 has 20 divisors (see below), whose sum is σ = 190126224. Its totient is φ = 32709824.

The previous prime is 81774631. The next prime is 81774659. The reversal of 81774640 is 4647718.

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

It is a self number, because there is not a number n which added to its sum of digits gives 81774640.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 511012 + ... + 511171.

Almost surely, 2^81774640 is an apocalyptic number.

81774640 is a gapful number since it is divisible by the number (80) formed by its first and last digit.

It is an amenable number.

81774640 is an abundant number, since it is smaller than the sum of its proper divisors (108351584).

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

81774640 is a wasteful number, since it uses less digits than its factorization.

81774640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1022196 (or 1022190 counting only the distinct ones).

The product of its (nonzero) digits is 37632, while the sum is 37.

The square root of 81774640 is about 9042.9331524677. The cubic root of 81774640 is about 434.0497865259.

It can be divided in two parts, 817 and 74640, that added together give a palindrome (75457).

The spelling of 81774640 in words is "eighty-one million, seven hundred seventy-four thousand, six hundred forty".