1261801615 has 4 divisors (see below), whose sum is σ = 1514161944. Its totient is φ = 1009441288.

The previous prime is 1261801601. The next prime is 1261801631. The reversal of 1261801615 is 5161081621.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 5161081621 = 67061 ⋅76961.

It is a cyclic number.

It is not a de Polignac number, because 1261801615 - 2¹⁵ = 1261768847 is a prime.

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 126180157 + ... + 126180166.

It is an arithmetic number, because the mean of its divisors is an integer number (378540486).

Almost surely, 2^1261801615 is an apocalyptic number.

1261801615 is a deficient number, since it is larger than the sum of its proper divisors (252360329).

1261801615 is an equidigital number, since it uses as much as digits as its factorization.

1261801615 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 252360328.

The product of its (nonzero) digits is 2880, while the sum is 31.

The square root of 1261801615 is about 35521.8470099740. The cubic root of 1261801615 is about 1080.5968394614.

The spelling of 1261801615 in words is "one billion, two hundred sixty-one million, eight hundred one thousand, six hundred fifteen".