6721981 has 8 divisors (see below), whose sum is σ = 7698240. Its totient is φ = 5749728.

The previous prime is 6721973. The next prime is 6721993. The reversal of 6721981 is 1891276.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 6721981 - 2³ = 6721973 is a prime.

It is a super-2 number, since 2×6721981² = 90370057128722, which contains 22 as substring.

It is an Ulam number.

It is a Duffinian number.

6721981 is a lucky number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (6721951) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 5070 + ... + 6256.

It is an arithmetic number, because the mean of its divisors is an integer number (962280).

Almost surely, 2^6721981 is an apocalyptic number.

It is an amenable number.

6721981 is a deficient number, since it is larger than the sum of its proper divisors (976259).

6721981 is a wasteful number, since it uses less digits than its factorization.

6721981 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2003.

The product of its digits is 6048, while the sum is 34.

The square root of 6721981 is about 2592.6783448781. The cubic root of 6721981 is about 188.7263005491.

The spelling of 6721981 in words is "six million, seven hundred twenty-one thousand, nine hundred eighty-one".