1221002020128 has 96 divisors (see below), whose sum is σ = 3496723921152. Its totient is φ = 369977529600.

The previous prime is 1221002020127. The next prime is 1221002020177. The reversal of 1221002020128 is 8210202001221.

It is a tau number, because it is divible by the number of its divisors (96).

It is not an unprimeable number, because it can be changed into a prime (1221002020127) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 25365363 + ... + 25413453.

It is an arithmetic number, because the mean of its divisors is an integer number (36424207512).

Almost surely, 2^{1221002020128} is an apocalyptic number.

It is an amenable number.

1221002020128 is an abundant number, since it is smaller than the sum of its proper divisors (2275721901024).

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

1221002020128 is a wasteful number, since it uses less digits than its factorization.

1221002020128 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 72158 (or 72150 counting only the distinct ones).

The product of its (nonzero) digits is 256, while the sum is 21.

Adding to 1221002020128 its reverse (8210202001221), we get a palindrome (9431204021349).

The spelling of 1221002020128 in words is "one trillion, two hundred twenty-one billion, two million, twenty thousand, one hundred twenty-eight".