6601981 has 4 divisors (see below), whose sum is σ = 6616764. Its totient is φ = 6587200.

The previous prime is 6601961. The next prime is 6601993. The reversal of 6601981 is 1891066.

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 793881 + 5808100 = 891^2 + 2410^2 .

It is a cyclic number.

It is not a de Polignac number, because 6601981 - 2¹⁹ = 6077693 is a prime.

It is a super-2 number, since 2×6601981² = 87172306248722, 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 (6601921) 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, 6700 + ... + 7621.

It is an arithmetic number, because the mean of its divisors is an integer number (1654191).

Almost surely, 2^6601981 is an apocalyptic number.

It is an amenable number.

6601981 is a deficient number, since it is larger than the sum of its proper divisors (14783).

6601981 is a wasteful number, since it uses less digits than its factorization.

6601981 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 14782.

The product of its (nonzero) digits is 2592, while the sum is 31.

The square root of 6601981 is about 2569.4320384085. The cubic root of 6601981 is about 187.5965109075.

Subtracting from 6601981 its reverse (1891066), we obtain a triangular number (4710915 = T₃₀₆₉).

The spelling of 6601981 in words is "six million, six hundred one thousand, nine hundred eighty-one".