81502640 has 40 divisors (see below), whose sum is σ = 191639520. Its totient is φ = 32231936.

The previous prime is 81502633. The next prime is 81502651. The reversal of 81502640 is 4620518.

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

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 7 ways as a sum of consecutive naturals, for example, 1397 + ... + 12843.

It is an arithmetic number, because the mean of its divisors is an integer number (4790988).

Almost surely, 2^81502640 is an apocalyptic number.

81502640 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 81502640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (95819760).

81502640 is an abundant number, since it is smaller than the sum of its proper divisors (110136880).

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

81502640 is a wasteful number, since it uses less digits than its factorization.

81502640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11549 (or 11543 counting only the distinct ones).

The product of its (nonzero) digits is 1920, while the sum is 26.

The square root of 81502640 is about 9027.8812575266. The cubic root of 81502640 is about 433.5680043837.

The spelling of 81502640 in words is "eighty-one million, five hundred two thousand, six hundred forty".