1211209999920 has 240 divisors, whose sum is σ = 4203930931200. Its totient is φ = 312192944640.

The previous prime is 1211209999913. The next prime is 1211209999921. The reversal of 1211209999920 is 299999021121.

It is a tau number, because it is divible by the number of its divisors (240).

It is not an unprimeable number, because it can be changed into a prime (1211209999921) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 18694141 + ... + 18758819.

It is an arithmetic number, because the mean of its divisors is an integer number (17516378880).

Almost surely, 2^{1211209999920} is an apocalyptic number.

1211209999920 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 1211209999920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (2101965465600).

1211209999920 is an abundant number, since it is smaller than the sum of its proper divisors (2992720931280).

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

1211209999920 is a wasteful number, since it uses less digits than its factorization.

1211209999920 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 65568 (or 65559 counting only the distinct ones).

The product of its (nonzero) digits is 472392, while the sum is 54.

The spelling of 1211209999920 in words is "one trillion, two hundred eleven billion, two hundred nine million, nine hundred ninety-nine thousand, nine hundred twenty".