6999921 has 6 divisors (see below), whose sum is σ = 10111010. Its totient is φ = 4666608.

The previous prime is 6999911. The next prime is 6999929. The reversal of 6999921 is 1299996.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 3629025 + 3370896 = 1905^2 + 1836^2 .

It is not a de Polignac number, because 6999921 - 2⁶ = 6999857 is a prime.

It is a Duffinian number.

6999921 is a lucky number.

It is not an unprimeable number, because it can be changed into a prime (6999929) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 388876 + ... + 388893.

Almost surely, 2^6999921 is an apocalyptic number.

It is an amenable number.

6999921 is a deficient number, since it is larger than the sum of its proper divisors (3111089).

6999921 is a wasteful number, since it uses less digits than its factorization.

6999921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 777775 (or 777772 counting only the distinct ones).

The product of its digits is 78732, while the sum is 45.

The square root of 6999921 is about 2645.7363814258. The cubic root of 6999921 is about 191.2923986480.

The spelling of 6999921 in words is "six million, nine hundred ninety-nine thousand, nine hundred twenty-one".