2251681 has 2 divisors, whose sum is σ = 2251682. Its totient is φ = 2251680.

The previous prime is 2251673. The next prime is 2251687. The reversal of 2251681 is 1861522.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 2250000 + 1681 = 1500^2 + 41^2 .

It is a cyclic number.

It is not a de Polignac number, because 2251681 - 2³ = 2251673 is a prime.

It is a super-2 number, since 2×2251681² = 10140134651522, which contains 22 as substring.

It is equal to p₁₆₆₁₈₃ and since 2251681 and 166183 have the same sum of digits, it is a Honaker prime.

It is not a weakly prime, because it can be changed into another prime (2251687) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1125840 + 1125841.

It is an arithmetic number, because the mean of its divisors is an integer number (1125841).

2^2251681 is an apocalyptic number.

It is an amenable number.

2251681 is a deficient number, since it is larger than the sum of its proper divisors (1).

2251681 is an equidigital number, since it uses as much as digits as its factorization.

2251681 is an evil number, because the sum of its binary digits is even.

The product of its digits is 960, while the sum is 25.

The square root of 2251681 is about 1500.5602287146. The cubic root of 2251681 is about 131.0696946706.

It can be divided in two parts, 225 and 1681, that multiplied together give a square (378225 = 615²).

The spelling of 2251681 in words is "two million, two hundred fifty-one thousand, six hundred eighty-one".