1261666137 has 4 divisors (see below), whose sum is σ = 1682221520. Its totient is φ = 841110756.

The previous prime is 1261666123. The next prime is 1261666157. The reversal of 1261666137 is 7316661621.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 1261666137 - 2⁷ = 1261666009 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 1261666095 and 1261666104.

It is not an unprimeable number, because it can be changed into a prime (1261666157) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 210277687 + ... + 210277692.

It is an arithmetic number, because the mean of its divisors is an integer number (420555380).

Almost surely, 2^1261666137 is an apocalyptic number.

It is an amenable number.

1261666137 is a deficient number, since it is larger than the sum of its proper divisors (420555383).

1261666137 is an equidigital number, since it uses as much as digits as its factorization.

1261666137 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 420555382.

The product of its digits is 54432, while the sum is 39.

The square root of 1261666137 is about 35519.9399915034. The cubic root of 1261666137 is about 1080.5581639843.

The spelling of 1261666137 in words is "one billion, two hundred sixty-one million, six hundred sixty-six thousand, one hundred thirty-seven".