1261565520 has 80 divisors (see below), whose sum is σ = 3922195392. Its totient is φ = 335441920.

The previous prime is 1261565507. The next prime is 1261565581. The reversal of 1261565520 is 255651621.

It is a tau number, because it is divible by the number of its divisors (80).

It is a super-2 number, since 2×1261565520² = 3183095122505740800, which contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 77275 + ... + 92165.

Almost surely, 2^1261565520 is an apocalyptic number.

1261565520 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 1261565520, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1961097696).

1261565520 is an abundant number, since it is smaller than the sum of its proper divisors (2660629872).

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

1261565520 is a wasteful number, since it uses less digits than its factorization.

1261565520 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 15260 (or 15254 counting only the distinct ones).

The product of its (nonzero) digits is 18000, while the sum is 33.

The square root of 1261565520 is about 35518.5236179659. The cubic root of 1261565520 is about 1080.5294386324.

The spelling of 1261565520 in words is "one billion, two hundred sixty-one million, five hundred sixty-five thousand, five hundred twenty".