1216559100 has 144 divisors (see below), whose sum is σ = 3745260288. Its totient is φ = 303836160.

The previous prime is 1216559087. The next prime is 1216559153. The reversal of 1216559100 is 19556121.

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 47 ways as a sum of consecutive naturals, for example, 1340847 + ... + 1341753.

It is an arithmetic number, because the mean of its divisors is an integer number (26008752).

Almost surely, 2^1216559100 is an apocalyptic number.

1216559100 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 1216559100, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1872630144).

1216559100 is an abundant number, since it is smaller than the sum of its proper divisors (2528701188).

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

1216559100 is a wasteful number, since it uses less digits than its factorization.

1216559100 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1204 (or 1197 counting only the distinct ones).

The product of its (nonzero) digits is 2700, while the sum is 30.

The square root of 1216559100 is about 34879.2072731018. The cubic root of 1216559100 is about 1067.5242203186.

The spelling of 1216559100 in words is "one billion, two hundred sixteen million, five hundred fifty-nine thousand, one hundred".