81718621 has 4 divisors (see below), whose sum is σ = 81777472. Its totient is φ = 81659772.

The previous prime is 81718577. The next prime is 81718649. The reversal of 81718621 is 12681718.

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.

It is a cyclic number.

It is not a de Polignac number, because 81718621 - 2¹⁷ = 81587549 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 (81718661) 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, 27291 + ... + 30136.

It is an arithmetic number, because the mean of its divisors is an integer number (20444368).

Almost surely, 2^81718621 is an apocalyptic number.

It is an amenable number.

81718621 is a deficient number, since it is larger than the sum of its proper divisors (58851).

81718621 is a wasteful number, since it uses less digits than its factorization.

81718621 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 58850.

The product of its digits is 5376, while the sum is 34.

The square root of 81718621 is about 9039.8352307993. The cubic root of 81718621 is about 433.9506498849.

The spelling of 81718621 in words is "eighty-one million, seven hundred eighteen thousand, six hundred twenty-one".