1261557780 has 48 divisors (see below), whose sum is σ = 4036986240. Its totient is φ = 288355968.

The previous prime is 1261557767. The next prime is 1261557793. The reversal of 1261557780 is 877551621.

It is an interprime number because it is at equal distance from previous prime (1261557767) and next prime (1261557793).

It is a Harshad number since it is a multiple of its sum of digits (42).

It is a congruent number.

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 15 ways as a sum of consecutive naturals, for example, 1501435 + ... + 1502274.

It is an arithmetic number, because the mean of its divisors is an integer number (84103880).

Almost surely, 2^1261557780 is an apocalyptic number.

1261557780 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

1261557780 is an abundant number, since it is smaller than the sum of its proper divisors (2775428460).

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

1261557780 is a wasteful number, since it uses less digits than its factorization.

1261557780 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3003728 (or 3003726 counting only the distinct ones).

The product of its (nonzero) digits is 117600, while the sum is 42.

The square root of 1261557780 is about 35518.4146605673. The cubic root of 1261557780 is about 1080.5272288608.

The spelling of 1261557780 in words is "one billion, two hundred sixty-one million, five hundred fifty-seven thousand, seven hundred eighty".