2159681 has 2 divisors, whose sum is σ = 2159682. Its totient is φ = 2159680.

The previous prime is 2159671. The next prime is 2159701. The reversal of 2159681 is 1869512.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 2146225 + 13456 = 1465^2 + 116^2 .

It is a cyclic number.

It is not a de Polignac number, because 2159681 - 2¹⁸ = 1897537 is a prime.

It is a super-2 number, since 2×2159681² = 9328444043522, which contains 22 as substring.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is a plaindrome in base 11.

It is not a weakly prime, because it can be changed into another prime (2159621) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1079840 + 1079841.

It is an arithmetic number, because the mean of its divisors is an integer number (1079841).

2^2159681 is an apocalyptic number.

It is an amenable number.

2159681 is a deficient number, since it is larger than the sum of its proper divisors (1).

2159681 is an equidigital number, since it uses as much as digits as its factorization.

2159681 is an evil number, because the sum of its binary digits is even.

The product of its digits is 4320, while the sum is 32.

The square root of 2159681 is about 1469.5853156588. The cubic root of 2159681 is about 129.2597175269.

The spelling of 2159681 in words is "two million, one hundred fifty-nine thousand, six hundred eighty-one".