6491981 has 4 divisors (see below), whose sum is σ = 6650364. Its totient is φ = 6333600.

The previous prime is 6491971. The next prime is 6491993. The reversal of 6491981 is 1891946.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 2669956 + 3822025 = 1634^2 + 1955^2 .

It is a cyclic number.

It is not a de Polignac number, because 6491981 - 2¹⁴ = 6475597 is a prime.

It is a super-2 number, since 2×6491981² = 84291634608722, which contains 22 as substring.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (6491951) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 79130 + ... + 79211.

It is an arithmetic number, because the mean of its divisors is an integer number (1662591).

Almost surely, 2^6491981 is an apocalyptic number.

It is an amenable number.

6491981 is a deficient number, since it is larger than the sum of its proper divisors (158383).

6491981 is a wasteful number, since it uses less digits than its factorization.

6491981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 158382.

The product of its digits is 15552, while the sum is 38.

The square root of 6491981 is about 2547.9366161661. The cubic root of 6491981 is about 186.5487800871.

The spelling of 6491981 in words is "six million, four hundred ninety-one thousand, nine hundred eighty-one".