81643245 has 16 divisors (see below), whose sum is σ = 130742592. Its totient is φ = 43505280.

The previous prime is 81643241. The next prime is 81643253. The reversal of 81643245 is 54234618.

It is not a de Polignac number, because 81643245 - 2² = 81643241 is a prime.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81643241) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 28530 + ... + 31260.

It is an arithmetic number, because the mean of its divisors is an integer number (8171412).

Almost surely, 2^81643245 is an apocalyptic number.

It is an amenable number.

81643245 is a deficient number, since it is larger than the sum of its proper divisors (49099347).

81643245 is a wasteful number, since it uses less digits than its factorization.

81643245 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4732.

The product of its digits is 23040, while the sum is 33.

The square root of 81643245 is about 9035.6651664390. The cubic root of 81643245 is about 433.8171857049.

The spelling of 81643245 in words is "eighty-one million, six hundred forty-three thousand, two hundred forty-five".