1261535601 has 24 divisors (see below), whose sum is σ = 1760893344. Its totient is φ = 802880320.

The previous prime is 1261535567. The next prime is 1261535621. The reversal of 1261535601 is 1065351621.

It is not a de Polignac number, because 1261535601 - 2¹⁰ = 1261534577 is a prime.

It is not an unprimeable number, because it can be changed into a prime (1261535621) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 269386 + ... + 274028.

It is an arithmetic number, because the mean of its divisors is an integer number (73370556).

Almost surely, 2^1261535601 is an apocalyptic number.

It is an amenable number.

1261535601 is a deficient number, since it is larger than the sum of its proper divisors (499357743).

1261535601 is an equidigital number, since it uses as much as digits as its factorization.

1261535601 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4781 (or 4734 counting only the distinct ones).

The product of its (nonzero) digits is 5400, while the sum is 30.

The square root of 1261535601 is about 35518.1024408681. The cubic root of 1261535601 is about 1080.5208967017.

The spelling of 1261535601 in words is "one billion, two hundred sixty-one million, five hundred thirty-five thousand, six hundred one".