6921197721 has 12 divisors (see below), whose sum is σ = 10014152148. Its totient is φ = 4606347264.

The previous prime is 6921197719. The next prime is 6921197729. The reversal of 6921197721 is 1277911296.

It can be written as a sum of positive squares in 2 ways, for example, as 4919619600 + 2001578121 = 70140^2 + 44739^2 .

It is not a de Polignac number, because 6921197721 - 2¹ = 6921197719 is a prime.

It is not an unprimeable number, because it can be changed into a prime (6921197729) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 643080 + ... + 653753.

It is an arithmetic number, because the mean of its divisors is an integer number (834512679).

Almost surely, 2^6921197721 is an apocalyptic number.

It is an amenable number.

6921197721 is a deficient number, since it is larger than the sum of its proper divisors (3092954427).

6921197721 is a wasteful number, since it uses less digits than its factorization.

6921197721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1297432 (or 1297429 counting only the distinct ones).

The product of its digits is 95256, while the sum is 45.

The square root of 6921197721 is about 83193.7360682882. The cubic root of 6921197721 is about 1905.7258225786.

The spelling of 6921197721 in words is "six billion, nine hundred twenty-one million, one hundred ninety-seven thousand, seven hundred twenty-one".