81997558 has 8 divisors (see below), whose sum is σ = 127237680. Its totient is φ = 39585000.

The previous prime is 81997543. The next prime is 81997561. The reversal of 81997558 is 85579918.

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

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 706818 + ... + 706933.

It is an arithmetic number, because the mean of its divisors is an integer number (15904710).

Almost surely, 2^81997558 is an apocalyptic number.

81997558 is a deficient number, since it is larger than the sum of its proper divisors (45240122).

81997558 is a wasteful number, since it uses less digits than its factorization.

81997558 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1413782.

The product of its digits is 907200, while the sum is 52.

The square root of 81997558 is about 9055.2503002402. The cubic root of 81997558 is about 434.4438358415.

The spelling of 81997558 in words is "eighty-one million, nine hundred ninety-seven thousand, five hundred fifty-eight".