81964999 has 4 divisors (see below), whose sum is σ = 82009336. Its totient is φ = 81920664.

The previous prime is 81964979. The next prime is 81965003. The reversal of 81964999 is 99946918.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 81964999 - 2²⁵ = 48410567 is a prime.

It is a super-2 number, since 2×81964999² = 13436522122140002, 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 (81964969) 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, 19269 + ... + 23134.

It is an arithmetic number, because the mean of its divisors is an integer number (20502334).

Almost surely, 2^81964999 is an apocalyptic number.

81964999 is a deficient number, since it is larger than the sum of its proper divisors (44337).

81964999 is a wasteful number, since it uses less digits than its factorization.

81964999 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 44336.

The product of its digits is 1259712, while the sum is 55.

The square root of 81964999 is about 9053.4523249421. The cubic root of 81964999 is about 434.3863262854.

The spelling of 81964999 in words is "eighty-one million, nine hundred sixty-four thousand, nine hundred ninety-nine".