81957989 has 8 divisors (see below), whose sum is σ = 83887488. Its totient is φ = 80036320.

The previous prime is 81957979. The next prime is 81958007. The reversal of 81957989 is 98975918.

81957989 = 107² + 108² + ... + 627².

It is a happy number.

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

It is a cyclic number.

It is not a de Polignac number, because 81957989 - 2¹⁶ = 81892453 is a prime.

It is a super-2 number, since 2×81957989² = 13434223921848242, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81957949) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 22814 + ... + 26160.

It is an arithmetic number, because the mean of its divisors is an integer number (10485936).

Almost surely, 2^81957989 is an apocalyptic number.

It is an amenable number.

81957989 is a deficient number, since it is larger than the sum of its proper divisors (1929499).

81957989 is a wasteful number, since it uses less digits than its factorization.

81957989 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3915.

The product of its digits is 1632960, while the sum is 56.

The square root of 81957989 is about 9053.0651715317. The cubic root of 81957989 is about 434.3739424021.

The spelling of 81957989 in words is "eighty-one million, nine hundred fifty-seven thousand, nine hundred eighty-nine".