81320638 has 8 divisors (see below), whose sum is σ = 139406832. Its totient is φ = 34851696.

The previous prime is 81320633. The next prime is 81320653. The reversal of 81320638 is 83602318.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a super-3 number, since 3×81320638³ (a number of 25 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81320633) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2904295 + ... + 2904322.

It is an arithmetic number, because the mean of its divisors is an integer number (17425854).

Almost surely, 2^81320638 is an apocalyptic number.

81320638 is a deficient number, since it is larger than the sum of its proper divisors (58086194).

81320638 is a wasteful number, since it uses less digits than its factorization.

81320638 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5808626.

The product of its (nonzero) digits is 6912, while the sum is 31.

The square root of 81320638 is about 9017.7956286445. The cubic root of 81320638 is about 433.2450330273.

The spelling of 81320638 in words is "eighty-one million, three hundred twenty thousand, six hundred thirty-eight".