6499981 has 4 divisors (see below), whose sum is σ = 6507612. Its totient is φ = 6492352.

The previous prime is 6499949. The next prime is 6499991. The reversal of 6499981 is 1899946.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 1899946 = 2 ⋅949973.

It can be written as a sum of positive squares in 2 ways, for example, as 2924100 + 3575881 = 1710^2 + 1891^2 .

It is a cyclic number.

It is not a de Polignac number, because 6499981 - 2⁵ = 6499949 is a prime.

It is a super-2 number, since 2×6499981² = 84499506000722, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (6499991) 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, 2350 + ... + 4303.

It is an arithmetic number, because the mean of its divisors is an integer number (1626903).

Almost surely, 2^6499981 is an apocalyptic number.

It is an amenable number.

6499981 is a deficient number, since it is larger than the sum of its proper divisors (7631).

6499981 is an equidigital number, since it uses as much as digits as its factorization.

6499981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7630.

The product of its digits is 139968, while the sum is 46.

The square root of 6499981 is about 2549.5060305871. The cubic root of 6499981 is about 186.6253760004.

The spelling of 6499981 in words is "six million, four hundred ninety-nine thousand, nine hundred eighty-one".