1261605220 has 12 divisors (see below), whose sum is σ = 2649371004. Its totient is φ = 504642080.

The previous prime is 1261605209. The next prime is 1261605271. The reversal of 1261605220 is 225061621.

It can be written as a sum of positive squares in 2 ways, for example, as 379158784 + 882446436 = 19472^2 + 29706^2 .

It is a super-2 number, since 2×1261605220² = 3183295462262496800, which contains 22 as substring.

It is an unprimeable number.

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 3 ways as a sum of consecutive naturals, for example, 31540111 + ... + 31540150.

It is an arithmetic number, because the mean of its divisors is an integer number (220780917).

Almost surely, 2^1261605220 is an apocalyptic number.

1261605220 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

1261605220 is an abundant number, since it is smaller than the sum of its proper divisors (1387765784).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

1261605220 is a wasteful number, since it uses less digits than its factorization.

1261605220 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 63080270 (or 63080268 counting only the distinct ones).

The product of its (nonzero) digits is 1440, while the sum is 25.

The square root of 1261605220 is about 35519.0824768884. The cubic root of 1261605220 is about 1080.5407728485.

Adding to 1261605220 its reverse (225061621), we get a palindrome (1486666841).

The spelling of 1261605220 in words is "one billion, two hundred sixty-one million, six hundred five thousand, two hundred twenty".