1261556601 has 16 divisors (see below), whose sum is σ = 1781412864. Its totient is φ = 792460944.

The previous prime is 1261556573. The next prime is 1261556603. The reversal of 1261556601 is 1066551621.

It is not a de Polignac number, because 1261556601 - 2⁶ = 1261556537 is a prime.

It is not an unprimeable number, because it can be changed into a prime (1261556603) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 131821 + ... + 141066.

It is an arithmetic number, because the mean of its divisors is an integer number (111338304).

Almost surely, 2^1261556601 is an apocalyptic number.

It is an amenable number.

1261556601 is a deficient number, since it is larger than the sum of its proper divisors (519856263).

1261556601 is a wasteful number, since it uses less digits than its factorization.

1261556601 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 272980.

The product of its (nonzero) digits is 10800, while the sum is 33.

The square root of 1261556601 is about 35518.3980635388. The cubic root of 1261556601 is about 1080.5268922553.

The spelling of 1261556601 in words is "one billion, two hundred sixty-one million, five hundred fifty-six thousand, six hundred one".