1261617813 has 12 divisors (see below), whose sum is σ = 1823035500. Its totient is φ = 840756096.

The previous prime is 1261617751. The next prime is 1261617869. The reversal of 1261617813 is 3187161621.

1261617813 is a `hidden beast` number, since 1 + 26 + 1 + 617 + 8 + 13 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 61826769 + 1199791044 = 7863^2 + 34638^2 .

It is not a de Polignac number, because 1261617813 - 2¹⁰ = 1261616789 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1261617713) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 756 + ... + 50237.

It is an arithmetic number, because the mean of its divisors is an integer number (151919625).

Almost surely, 2^1261617813 is an apocalyptic number.

It is an amenable number.

1261617813 is a deficient number, since it is larger than the sum of its proper divisors (561417687).

1261617813 is a wasteful number, since it uses less digits than its factorization.

1261617813 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 53748 (or 53745 counting only the distinct ones).

The product of its digits is 12096, while the sum is 36.

The square root of 1261617813 is about 35519.2597473540. The cubic root of 1261617813 is about 1080.5443680579.

The spelling of 1261617813 in words is "one billion, two hundred sixty-one million, six hundred seventeen thousand, eight hundred thirteen".