81321633 has 12 divisors (see below), whose sum is σ = 117994240. Its totient is φ = 53969976.

The previous prime is 81321619. The next prime is 81321637. The reversal of 81321633 is 33612318.

It is a happy number.

81321633 is a `hidden beast` number, since 8 + 1 + 3 + 21 + 633 = 666.

It is not a de Polignac number, because 81321633 - 2⁸ = 81321377 is a prime.

It is a super-2 number, since 2×81321633² = 13226415987573378, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 81321597 and 81321606.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81321637) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 18253 + ... + 22266.

Almost surely, 2^81321633 is an apocalyptic number.

It is an amenable number.

81321633 is a deficient number, since it is larger than the sum of its proper divisors (36672607).

81321633 is a wasteful number, since it uses less digits than its factorization.

81321633 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 40748 (or 40745 counting only the distinct ones).

The product of its digits is 2592, while the sum is 27.

The square root of 81321633 is about 9017.8507971689. The cubic root of 81321633 is about 433.2468000124.

The spelling of 81321633 in words is "eighty-one million, three hundred twenty-one thousand, six hundred thirty-three".