7128121 has 16 divisors (see below), whose sum is σ = 9571968. Its totient is φ = 5126400.

The previous prime is 7128101. The next prime is 7128139. The reversal of 7128121 is 1218217.

7128121 = T₇₈ + T₇₉ + ... + T₃₅₀.

7128121 = 134² + 135² + ... + 287².

It is a cyclic number.

It is not a de Polignac number, because 7128121 - 2⁷ = 7127993 is a prime.

7128121 is a lucky number.

It is a junction number, because it is equal to n+sod(n) for n = 7128092 and 7128101.

It is not an unprimeable number, because it can be changed into a prime (7128101) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 2560 + ... + 4561.

It is an arithmetic number, because the mean of its divisors is an integer number (598248).

Almost surely, 2^7128121 is an apocalyptic number.

It is an amenable number.

7128121 is a deficient number, since it is larger than the sum of its proper divisors (2443847).

7128121 is a wasteful number, since it uses less digits than its factorization.

7128121 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7152.

The product of its digits is 224, while the sum is 22.

The square root of 7128121 is about 2669.8541158648. The cubic root of 7128121 is about 192.4531487713.

The spelling of 7128121 in words is "seven million, one hundred twenty-eight thousand, one hundred twenty-one".