81816247 has 4 divisors (see below), whose sum is σ = 82183360. Its totient is φ = 81449136.

The previous prime is 81816239. The next prime is 81816269. The reversal of 81816247 is 74261818.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 74261818 = 2 ⋅37130909.

It is a cyclic number.

It is not a de Polignac number, because 81816247 - 2³ = 81816239 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81826247) 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, 183222 + ... + 183667.

It is an arithmetic number, because the mean of its divisors is an integer number (20545840).

Almost surely, 2^81816247 is an apocalyptic number.

81816247 is a deficient number, since it is larger than the sum of its proper divisors (367113).

81816247 is a wasteful number, since it uses less digits than its factorization.

81816247 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 367112.

The product of its digits is 21504, while the sum is 37.

The square root of 81816247 is about 9045.2333856015. The cubic root of 81816247 is about 434.1233889999.

The spelling of 81816247 in words is "eighty-one million, eight hundred sixteen thousand, two hundred forty-seven".