20011221128 has 8 divisors (see below), whose sum is σ = 37521039630. Its totient is φ = 10005610560.

The previous prime is 20011221127. The next prime is 20011221137. The reversal of 20011221128 is 82112211002.

It can be written as a sum of positive squares in only one way, i.e., 18664477924 + 1346743204 = 136618^2 + 36698^2 .

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

It is not an unprimeable number, because it can be changed into a prime (20011221127) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1250701313 + ... + 1250701328.

Almost surely, 2^20011221128 is an apocalyptic number.

It is an amenable number.

20011221128 is a deficient number, since it is larger than the sum of its proper divisors (17509818502).

20011221128 is a wasteful number, since it uses less digits than its factorization.

20011221128 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2501402647 (or 2501402643 counting only the distinct ones).

The product of its (nonzero) digits is 128, while the sum is 20.

The spelling of 20011221128 in words is "twenty billion, eleven million, two hundred twenty-one thousand, one hundred twenty-eight".