1261566461 has 4 divisors (see below), whose sum is σ = 1270033500. Its totient is φ = 1253099424.

The previous prime is 1261566443. The next prime is 1261566499. The reversal of 1261566461 is 1646651621.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 1646651621 = 2221 ⋅741401.

It can be written as a sum of positive squares in 2 ways, for example, as 223502500 + 1038063961 = 14950^2 + 32219^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1261566461 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 (1261566401) 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, 4233296 + ... + 4233593.

It is an arithmetic number, because the mean of its divisors is an integer number (317508375).

Almost surely, 2^1261566461 is an apocalyptic number.

It is an amenable number.

1261566461 is a deficient number, since it is larger than the sum of its proper divisors (8467039).

1261566461 is an equidigital number, since it uses as much as digits as its factorization.

1261566461 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8467038.

The product of its digits is 51840, while the sum is 38.

The square root of 1261566461 is about 35518.5368645726. The cubic root of 1261566461 is about 1080.5297072875.

The spelling of 1261566461 in words is "one billion, two hundred sixty-one million, five hundred sixty-six thousand, four hundred sixty-one".