1261665858 has 16 divisors (see below), whose sum is σ = 2584876896. Its totient is φ = 410297760.

The previous prime is 1261665857. The next prime is 1261665883. The reversal of 1261665858 is 8585661621.

It is not an unprimeable number, because it can be changed into a prime (1261665857) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2564116 + ... + 2564607.

It is an arithmetic number, because the mean of its divisors is an integer number (161554806).

Almost surely, 2^1261665858 is an apocalyptic number.

1261665858 is an abundant number, since it is smaller than the sum of its proper divisors (1323211038).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

1261665858 is a wasteful number, since it uses less digits than its factorization.

1261665858 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5128769.

The product of its digits is 691200, while the sum is 48.

The square root of 1261665858 is about 35519.9360641316. The cubic root of 1261665858 is about 1080.5580843341.

It can be divided in two parts, 1261 and 665858, that multiplied together give a palindrome (839646938).

The spelling of 1261665858 in words is "one billion, two hundred sixty-one million, six hundred sixty-five thousand, eight hundred fifty-eight".