1261257781 has 8 divisors (see below), whose sum is σ = 1462952000. Its totient is φ = 1064942208.

The previous prime is 1261257721. The next prime is 1261257787. The reversal of 1261257781 is 1877521621.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 1261257781 - 2⁷ = 1261257653 is a prime.

It is a super-2 number, since 2×1261257781² = 3181542380266087922, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1261257787) 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, 1344156 + ... + 1345093.

It is an arithmetic number, because the mean of its divisors is an integer number (182869000).

Almost surely, 2^1261257781 is an apocalyptic number.

It is an amenable number.

1261257781 is a deficient number, since it is larger than the sum of its proper divisors (201694219).

1261257781 is an equidigital number, since it uses as much as digits as its factorization.

1261257781 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2689323.

The product of its digits is 47040, while the sum is 40.

The square root of 1261257781 is about 35514.1912620856. The cubic root of 1261257781 is about 1080.4415721192.

The spelling of 1261257781 in words is "one billion, two hundred sixty-one million, two hundred fifty-seven thousand, seven hundred eighty-one".