6651981 has 24 divisors (see below), whose sum is σ = 11628864. Its totient is φ = 3576960.

The previous prime is 6651959. The next prime is 6652001. The reversal of 6651981 is 1891566.

6651981 is a `hidden beast` number, since 66 + 519 + 81 = 666.

It is not a de Polignac number, because 6651981 - 2¹³ = 6643789 is a prime.

It is a super-2 number, since 2×6651981² = 88497702448722, 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 (6651941) 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, 2035 + ... + 4176.

It is an arithmetic number, because the mean of its divisors is an integer number (484536).

Almost surely, 2^6651981 is an apocalyptic number.

It is an amenable number.

6651981 is a deficient number, since it is larger than the sum of its proper divisors (4976883).

6651981 is a wasteful number, since it uses less digits than its factorization.

6651981 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6241 (or 6238 counting only the distinct ones).

The product of its digits is 12960, while the sum is 36.

The square root of 6651981 is about 2579.1434624697. The cubic root of 6651981 is about 188.0689067614.

The spelling of 6651981 in words is "six million, six hundred fifty-one thousand, nine hundred eighty-one".