81400805 has 4 divisors (see below), whose sum is σ = 97680972. Its totient is φ = 65120640.

The previous prime is 81400801. The next prime is 81400817. The reversal of 81400805 is 50800418.

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 47306884 + 34093921 = 6878^2 + 5839^2 .

It is not a de Polignac number, because 81400805 - 2² = 81400801 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81400801) 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, 8140076 + ... + 8140085.

It is an arithmetic number, because the mean of its divisors is an integer number (24420243).

Almost surely, 2^81400805 is an apocalyptic number.

It is an amenable number.

81400805 is a deficient number, since it is larger than the sum of its proper divisors (16280167).

81400805 is a wasteful number, since it uses less digits than its factorization.

81400805 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16280166.

The product of its (nonzero) digits is 1280, while the sum is 26.

The square root of 81400805 is about 9022.2394670060. The cubic root of 81400805 is about 433.3873525688.

The spelling of 81400805 in words is "eighty-one million, four hundred thousand, eight hundred five".