1211981780 has 24 divisors (see below), whose sum is σ = 2655821952. Its totient is φ = 463714592.

The previous prime is 1211981779. The next prime is 1211981801. The reversal of 1211981780 is 871891121.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1316912 + ... + 1317831.

It is an arithmetic number, because the mean of its divisors is an integer number (110659248).

Almost surely, 2^1211981780 is an apocalyptic number.

1211981780 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

1211981780 is an abundant number, since it is smaller than the sum of its proper divisors (1443840172).

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

1211981780 is a wasteful number, since it uses less digits than its factorization.

1211981780 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2634775 (or 2634773 counting only the distinct ones).

The product of its (nonzero) digits is 8064, while the sum is 38.

The square root of 1211981780 is about 34813.5286921622. The cubic root of 1211981780 is about 1066.1836795567.

The spelling of 1211981780 in words is "one billion, two hundred eleven million, nine hundred eighty-one thousand, seven hundred eighty".