6921572121 has 8 divisors (see below), whose sum is σ = 10254180960. Its totient is φ = 4614381396.

The previous prime is 6921572113. The next prime is 6921572173. The reversal of 6921572121 is 1212751296.

6921572121 is a `hidden beast` number, since 69 + 2 + 1 + 572 + 1 + 21 = 666.

It is not a de Polignac number, because 6921572121 - 2³ = 6921572113 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (6921572221) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 128177235 + ... + 128177288.

It is an arithmetic number, because the mean of its divisors is an integer number (1281772620).

Almost surely, 2^6921572121 is an apocalyptic number.

It is an amenable number.

6921572121 is a deficient number, since it is larger than the sum of its proper divisors (3332608839).

6921572121 is a wasteful number, since it uses less digits than its factorization.

6921572121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 256354532 (or 256354526 counting only the distinct ones).

The product of its digits is 15120, while the sum is 36.

The square root of 6921572121 is about 83195.9862072684. The cubic root of 6921572121 is about 1905.7601851708.

The spelling of 6921572121 in words is "six billion, nine hundred twenty-one million, five hundred seventy-two thousand, one hundred twenty-one".