81749520 has 80 divisors (see below), whose sum is σ = 281589120. Its totient is φ = 21799296.

The previous prime is 81749513. The next prime is 81749527. The reversal of 81749520 is 2594718.

It is an interprime number because it is at equal distance from previous prime (81749513) and next prime (81749527).

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

It is a Harshad number since it is a multiple of its sum of digits (36).

It is not an unprimeable number, because it can be changed into a prime (81749527) by changing a digit.

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, 16764 + ... + 21083.

It is an arithmetic number, because the mean of its divisors is an integer number (3519864).

Almost surely, 2^81749520 is an apocalyptic number.

81749520 is a gapful number since it is divisible by the number (80) formed by its first and last digit.

It is an amenable number.

81749520 is an abundant number, since it is smaller than the sum of its proper divisors (199839600).

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

81749520 is a wasteful number, since it uses less digits than its factorization.

81749520 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 37869 (or 37857 counting only the distinct ones).

The product of its (nonzero) digits is 20160, while the sum is 36.

The square root of 81749520 is about 9041.5441159129. The cubic root of 81749520 is about 434.0053373451.

The spelling of 81749520 in words is "eighty-one million, seven hundred forty-nine thousand, five hundred twenty".