81749280 has 96 divisors (see below), whose sum is σ = 264527424. Its totient is φ = 21206016.

The previous prime is 81749257. The next prime is 81749303. The reversal of 81749280 is 8294718.

It is an interprime number because it is at equal distance from previous prime (81749257) and next prime (81749303).

It is a tau number, because it is divible by the number of its divisors (96).

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 15 ways as a sum of consecutive naturals, for example, 15459 + ... + 20061.

It is an arithmetic number, because the mean of its divisors is an integer number (2755494).

Almost surely, 2^81749280 is an apocalyptic number.

81749280 is a gapful number since it is divisible by the number (80) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81749280, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (132263712).

81749280 is an abundant number, since it is smaller than the sum of its proper divisors (182778144).

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

81749280 is a wasteful number, since it uses less digits than its factorization.

81749280 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4658 (or 4650 counting only the distinct ones).

The product of its (nonzero) digits is 32256, while the sum is 39.

The square root of 81749280 is about 9041.5308438339. The cubic root of 81749280 is about 434.0049126275.

The spelling of 81749280 in words is "eighty-one million, seven hundred forty-nine thousand, two hundred eighty".