817661 has 4 divisors (see below), whose sum is σ = 880572. Its totient is φ = 754752.

The previous prime is 817651. The next prime is 817669. The reversal of 817661 is 166718.

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 319225 + 498436 = 565^2 + 706^2 .

It is a cyclic number.

It is not a de Polignac number, because 817661 - 2¹⁴ = 801277 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 (817669) 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, 31436 + ... + 31461.

It is an arithmetic number, because the mean of its divisors is an integer number (220143).

2⁸¹⁷⁶⁶¹ is an apocalyptic number.

It is an amenable number.

817661 is a deficient number, since it is larger than the sum of its proper divisors (62911).

817661 is a wasteful number, since it uses less digits than its factorization.

817661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 62910.

The product of its digits is 2016, while the sum is 29.

The square root of 817661 is about 904.2460948215. The cubic root of 817661 is about 93.5099363171.

The spelling of 817661 in words is "eight hundred seventeen thousand, six hundred sixty-one".