81907201 has 4 divisors (see below), whose sum is σ = 83250004. Its totient is φ = 80564400.

The previous prime is 81907187. The next prime is 81907211. The reversal of 81907201 is 10270918.

81907201 = 6399² + 6400².

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 40947201 + 40960000 = 6399^2 + 6400^2 .

It is a cyclic number.

It is not a de Polignac number, because 81907201 - 2⁹ = 81906689 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 81907201.

It is not an unprimeable number, because it can be changed into a prime (81907211) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 671310 + ... + 671431.

It is an arithmetic number, because the mean of its divisors is an integer number (20812501).

Almost surely, 2^81907201 is an apocalyptic number.

81907201 is the 6400-th centered square number.

It is an amenable number.

81907201 is a deficient number, since it is larger than the sum of its proper divisors (1342803).

81907201 is a wasteful number, since it uses less digits than its factorization.

81907201 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1342802.

The product of its (nonzero) digits is 1008, while the sum is 28.

The square root of 81907201 is about 9050.2597200301. The cubic root of 81907201 is about 434.2841990975.

The spelling of 81907201 in words is "eighty-one million, nine hundred seven thousand, two hundred one".