1261661520 has 160 divisors (see below), whose sum is σ = 4590920448. Its totient is φ = 280571904.

The previous prime is 1261661519. The next prime is 1261661539. The reversal of 1261661520 is 251661621.

1261661520 is digitally balanced in base 6, because in such base it contains all the possibile digits an equal number of times.

It is a Harshad number since it is a multiple of its sum of digits (30).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 52012 + ... + 72308.

Almost surely, 2^1261661520 is an apocalyptic number.

1261661520 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 1261661520, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (2295460224).

1261661520 is an abundant number, since it is smaller than the sum of its proper divisors (3329258928).

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

1261661520 is a wasteful number, since it uses less digits than its factorization.

1261661520 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 20357 (or 20351 counting only the distinct ones).

The product of its (nonzero) digits is 4320, while the sum is 30.

The square root of 1261661520 is about 35519.8749997801. The cubic root of 1261661520 is about 1080.5568459010.

The spelling of 1261661520 in words is "one billion, two hundred sixty-one million, six hundred sixty-one thousand, five hundred twenty".