81489720 has 64 divisors (see below), whose sum is σ = 263279520. Its totient is φ = 20058624.

The previous prime is 81489703. The next prime is 81489763. The reversal of 81489720 is 2798418.

It is a Harshad number since it is a multiple of its sum of digits (39).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 24559 + ... + 27678.

Almost surely, 2^81489720 is an apocalyptic number.

It is an amenable number.

81489720 is an abundant number, since it is smaller than the sum of its proper divisors (181789800).

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

81489720 is a wasteful number, since it uses less digits than its factorization.

81489720 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 52264 (or 52260 counting only the distinct ones).

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

The square root of 81489720 is about 9027.1656681375. The cubic root of 81489720 is about 433.5450930824.

The spelling of 81489720 in words is "eighty-one million, four hundred eighty-nine thousand, seven hundred twenty".