81742981 has 4 divisors (see below), whose sum is σ = 82331200. Its totient is φ = 81154764.

The previous prime is 81742979. The next prime is 81743017. The reversal of 81742981 is 18924718.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 18924718 = 2 ⋅9462359.

It is a cyclic number.

It is not a de Polignac number, because 81742981 - 2¹ = 81742979 is a prime.

It is a super-2 number, since 2×81742981² = 13363829885532722, 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 (81742901) 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, 293901 + ... + 294178.

It is an arithmetic number, because the mean of its divisors is an integer number (20582800).

Almost surely, 2^81742981 is an apocalyptic number.

It is an amenable number.

81742981 is a deficient number, since it is larger than the sum of its proper divisors (588219).

81742981 is a wasteful number, since it uses less digits than its factorization.

81742981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 588218.

The product of its digits is 32256, while the sum is 40.

The square root of 81742981 is about 9041.1825000937. The cubic root of 81742981 is about 433.9937652626.

The spelling of 81742981 in words is "eighty-one million, seven hundred forty-two thousand, nine hundred eighty-one".