817400721 has 4 divisors (see below), whose sum is σ = 1089867632. Its totient is φ = 544933812.

The previous prime is 817400719. The next prime is 817400743. The reversal of 817400721 is 127004718.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 817400721 - 2¹ = 817400719 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (817400621) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 136233451 + ... + 136233456.

It is an arithmetic number, because the mean of its divisors is an integer number (272466908).

Almost surely, 2^817400721 is an apocalyptic number.

It is an amenable number.

817400721 is a deficient number, since it is larger than the sum of its proper divisors (272466911).

817400721 is a wasteful number, since it uses less digits than its factorization.

817400721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 272466910.

The product of its (nonzero) digits is 3136, while the sum is 30.

The square root of 817400721 is about 28590.2207231774. The cubic root of 817400721 is about 935.0001319264. Note that the first 3 decimals are identical.

The spelling of 817400721 in words is "eight hundred seventeen million, four hundred thousand, seven hundred twenty-one".