2156721128 has 8 divisors (see below), whose sum is σ = 4043852130. Its totient is φ = 1078360560.

The previous prime is 2156721121. The next prime is 2156721163. The reversal of 2156721128 is 8211276512.

It can be written as a sum of positive squares in only one way, i.e., 1819704964 + 337016164 = 42658^2 + 18358^2 .

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 (2156721121) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 134795063 + ... + 134795078.

Almost surely, 2^2156721128 is an apocalyptic number.

It is an amenable number.

2156721128 is a deficient number, since it is larger than the sum of its proper divisors (1887131002).

2156721128 is a wasteful number, since it uses less digits than its factorization.

2156721128 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 269590147 (or 269590143 counting only the distinct ones).

The product of its digits is 13440, while the sum is 35.

The square root of 2156721128 is about 46440.5117112204. The cubic root of 2156721128 is about 1292.0063979976.

The spelling of 2156721128 in words is "two billion, one hundred fifty-six million, seven hundred twenty-one thousand, one hundred twenty-eight".