20121221128 has 8 divisors (see below), whose sum is σ = 37727289630. Its totient is φ = 10060610560.

The previous prime is 20121221117. The next prime is 20121221129. The reversal of 20121221128 is 82112212102.

It can be written as a sum of positive squares in only one way, i.e., 19600560004 + 520661124 = 140002^2 + 22818^2 .

It is a tau number, because it is divible by the number of its divisors (8).

It is a junction number, because it is equal to n+sod(n) for n = 20121221099 and 20121221108.

It is not an unprimeable number, because it can be changed into a prime (20121221129) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1257576313 + ... + 1257576328.

Almost surely, 2^20121221128 is an apocalyptic number.

It is an amenable number.

20121221128 is a deficient number, since it is larger than the sum of its proper divisors (17606068502).

20121221128 is a wasteful number, since it uses less digits than its factorization.

20121221128 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2515152647 (or 2515152643 counting only the distinct ones).

The product of its (nonzero) digits is 256, while the sum is 22.

The spelling of 20121221128 in words is "twenty billion, one hundred twenty-one million, two hundred twenty-one thousand, one hundred twenty-eight".