81549720 has 384 divisors, whose sum is σ = 334886400. Its totient is φ = 17563392.

The previous prime is 81549703. The next prime is 81549733. The reversal of 81549720 is 2794518.

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

It is a congruent number.

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 95 ways as a sum of consecutive naturals, for example, 1217127 + ... + 1217193.

It is an arithmetic number, because the mean of its divisors is an integer number (872100).

Almost surely, 2^81549720 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81549720, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (167443200).

81549720 is an abundant number, since it is smaller than the sum of its proper divisors (253336680).

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

81549720 is a wasteful number, since it uses less digits than its factorization.

81549720 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 124 (or 107 counting only the distinct ones).

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

The square root of 81549720 is about 9030.4883588874. The cubic root of 81549720 is about 433.6514718334.

The spelling of 81549720 in words is "eighty-one million, five hundred forty-nine thousand, seven hundred twenty".