81821207 has 4 divisors (see below), whose sum is σ = 88115160. Its totient is φ = 75527256.

The previous prime is 81821197. The next prime is 81821213. The reversal of 81821207 is 70212818.

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

It is a cyclic number.

It is not a de Polignac number, because 81821207 - 2¹⁰ = 81820183 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 81821207.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81821227) 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, 3146957 + ... + 3146982.

It is an arithmetic number, because the mean of its divisors is an integer number (22028790).

Almost surely, 2^81821207 is an apocalyptic number.

81821207 is a deficient number, since it is larger than the sum of its proper divisors (6293953).

81821207 is a wasteful number, since it uses less digits than its factorization.

81821207 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6293952.

The product of its (nonzero) digits is 1792, while the sum is 29.

The square root of 81821207 is about 9045.5075590041. The cubic root of 81821207 is about 434.1321615382.

It can be divided in two parts, 81821 and 207, that added together give a palindrome (82028).

The spelling of 81821207 in words is "eighty-one million, eight hundred twenty-one thousand, two hundred seven".