6921981 has 24 divisors (see below), whose sum is σ = 11288160. Its totient is φ = 4048800.

The previous prime is 6921961. The next prime is 6922001. The reversal of 6921981 is 1891296.

It is an interprime number because it is at equal distance from previous prime (6921961) and next prime (6922001).

It is not a de Polignac number, because 6921981 - 2⁵ = 6921949 is a prime.

It is a super-2 number, since 2×6921981² = 95827641928722, which contains 22 as substring.

6921981 is a lucky number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (6921961) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 1666 + ... + 4076.

It is an arithmetic number, because the mean of its divisors is an integer number (470340).

Almost surely, 2^6921981 is an apocalyptic number.

It is an amenable number.

6921981 is a deficient number, since it is larger than the sum of its proper divisors (4366179).

6921981 is a wasteful number, since it uses less digits than its factorization.

6921981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2457 (or 2454 counting only the distinct ones).

The product of its digits is 7776, while the sum is 36.

The square root of 6921981 is about 2630.9657922520. The cubic root of 6921981 is about 190.5797710845.

The spelling of 6921981 in words is "six million, nine hundred twenty-one thousand, nine hundred eighty-one".