815641261 has 4 divisors (see below), whose sum is σ = 817426492. Its totient is φ = 813856032.

The previous prime is 815641259. The next prime is 815641273. The reversal of 815641261 is 162146518.

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 272052036 + 543589225 = 16494^2 + 23315^2 .

It is a cyclic number.

It is not a de Polignac number, because 815641261 - 2¹ = 815641259 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 (815641231) 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, 891930 + ... + 892843.

It is an arithmetic number, because the mean of its divisors is an integer number (204356623).

Almost surely, 2^815641261 is an apocalyptic number.

It is an amenable number.

815641261 is a deficient number, since it is larger than the sum of its proper divisors (1785231).

815641261 is a wasteful number, since it uses less digits than its factorization.

815641261 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1785230.

The product of its digits is 11520, while the sum is 34.

The square root of 815641261 is about 28559.4338354247. The cubic root of 815641261 is about 934.3287855220.

Adding to 815641261 its reverse (162146518), we get a palindrome (977787779).

The spelling of 815641261 in words is "eight hundred fifteen million, six hundred forty-one thousand, two hundred sixty-one".