81337621 has 4 divisors (see below), whose sum is σ = 81531244. Its totient is φ = 81144000.

The previous prime is 81337609. The next prime is 81337631. The reversal of 81337621 is 12673318.

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

It can be written as a sum of positive squares in 2 ways, for example, as 12215025 + 69122596 = 3495^2 + 8314^2 .

It is a cyclic number.

It is not a de Polignac number, because 81337621 - 2¹³ = 81329429 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 (81337601) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 96180 + ... + 97021.

It is an arithmetic number, because the mean of its divisors is an integer number (20382811).

Almost surely, 2^81337621 is an apocalyptic number.

It is an amenable number.

81337621 is a deficient number, since it is larger than the sum of its proper divisors (193623).

81337621 is a wasteful number, since it uses less digits than its factorization.

81337621 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 193622.

The product of its digits is 6048, while the sum is 31.

The square root of 81337621 is about 9018.7372175932. The cubic root of 81337621 is about 433.2751905553.

The spelling of 81337621 in words is "eighty-one million, three hundred thirty-seven thousand, six hundred twenty-one".