1261016661 has 8 divisors (see below), whose sum is σ = 1681522560. Its totient is φ = 840594272.

The previous prime is 1261016639. The next prime is 1261016671. The reversal of 1261016661 is 1666101621.

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 1261016661 - 2¹¹ = 1261014613 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1261016671) 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, 38425 + ... + 63233.

It is an arithmetic number, because the mean of its divisors is an integer number (210190320).

Almost surely, 2^1261016661 is an apocalyptic number.

It is an amenable number.

1261016661 is a deficient number, since it is larger than the sum of its proper divisors (420505899).

1261016661 is a wasteful number, since it uses less digits than its factorization.

1261016661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 41755.

The product of its (nonzero) digits is 2592, while the sum is 30.

The square root of 1261016661 is about 35510.7964005315. The cubic root of 1261016661 is about 1080.3727168651.

The spelling of 1261016661 in words is "one billion, two hundred sixty-one million, sixteen thousand, six hundred sixty-one".