81810401 has 4 divisors (see below), whose sum is σ = 81834900. Its totient is φ = 81785904.

The previous prime is 81810373. The next prime is 81810419. The reversal of 81810401 is 10401818.

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 27050401 + 54760000 = 5201^2 + 7400^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81810401 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81810431) 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, 6266 + ... + 14243.

It is an arithmetic number, because the mean of its divisors is an integer number (20458725).

Almost surely, 2^81810401 is an apocalyptic number.

It is an amenable number.

81810401 is a deficient number, since it is larger than the sum of its proper divisors (24499).

81810401 is a wasteful number, since it uses less digits than its factorization.

81810401 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 24498.

The product of its (nonzero) digits is 256, while the sum is 23.

The square root of 81810401 is about 9044.9102261990. The cubic root of 81810401 is about 434.1130489762.

The spelling of 81810401 in words is "eighty-one million, eight hundred ten thousand, four hundred one".