1261866636242 has 4 divisors (see below), whose sum is σ = 1892799954366. Its totient is φ = 630933318120.

The previous prime is 1261866636211. The next prime is 1261866636287. The reversal of 1261866636242 is 2426366681621.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in only one way, i.e., 890986854241 + 370879782001 = 943921^2 + 608999^2 .

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 315466659059 + ... + 315466659062.

Almost surely, 2^{1261866636242} is an apocalyptic number.

1261866636242 is a deficient number, since it is larger than the sum of its proper divisors (630933318124).

1261866636242 is an equidigital number, since it uses as much as digits as its factorization.

1261866636242 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 630933318123.

The product of its digits is 5971968, while the sum is 53.

The spelling of 1261866636242 in words is "one trillion, two hundred sixty-one billion, eight hundred sixty-six million, six hundred thirty-six thousand, two hundred forty-two".