81722981 has 8 divisors (see below), whose sum is σ = 83875584. Its totient is φ = 79596720.

The previous prime is 81722969. The next prime is 81723041. The reversal of 81722981 is 18922718.

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 81722981 - 2¹⁰ = 81721957 is a prime.

It is a super-2 number, since 2×81722981² = 13357291247052722, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81722911) 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, 221 + ... + 12786.

It is an arithmetic number, because the mean of its divisors is an integer number (10484448).

Almost surely, 2^81722981 is an apocalyptic number.

It is an amenable number.

81722981 is a deficient number, since it is larger than the sum of its proper divisors (2152603).

81722981 is a wasteful number, since it uses less digits than its factorization.

81722981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 13171.

The product of its digits is 16128, while the sum is 38.

The square root of 81722981 is about 9040.0763824207. The cubic root of 81722981 is about 433.9583673883.

The spelling of 81722981 in words is "eighty-one million, seven hundred twenty-two thousand, nine hundred eighty-one".