1261245521 has 4 divisors (see below), whose sum is σ = 1335436452. Its totient is φ = 1187054592.

The previous prime is 1261245511. The next prime is 1261245523. The reversal of 1261245521 is 1255421621.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 1139805121 + 121440400 = 33761^2 + 11020^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1261245521 is a prime.

It is a super-2 number, since 2×1261245521² = 3181480528485122882, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (1261245523) 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 3 ways as a sum of consecutive naturals, for example, 37095440 + ... + 37095473.

It is an arithmetic number, because the mean of its divisors is an integer number (333859113).

Almost surely, 2^1261245521 is an apocalyptic number.

It is an amenable number.

1261245521 is a deficient number, since it is larger than the sum of its proper divisors (74190931).

1261245521 is an equidigital number, since it uses as much as digits as its factorization.

1261245521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 74190930.

The product of its digits is 4800, while the sum is 29.

The square root of 1261245521 is about 35514.0186546102. The cubic root of 1261245521 is about 1080.4380713131.

The spelling of 1261245521 in words is "one billion, two hundred sixty-one million, two hundred forty-five thousand, five hundred twenty-one".