1661281 has 2 divisors, whose sum is σ = 1661282. Its totient is φ = 1661280.

The previous prime is 1661273. The next prime is 1661293. The reversal of 1661281 is 1821661.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1083681 + 577600 = 1041^2 + 760^2 .

It is a cyclic number.

It is not a de Polignac number, because 1661281 - 2³ = 1661273 is a prime.

It is a super-2 number, since 2×1661281² = 5519709121922, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (1661251) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 830640 + 830641.

It is an arithmetic number, because the mean of its divisors is an integer number (830641).

2^1661281 is an apocalyptic number.

It is an amenable number.

1661281 is a deficient number, since it is larger than the sum of its proper divisors (1).

1661281 is an equidigital number, since it uses as much as digits as its factorization.

1661281 is an evil number, because the sum of its binary digits is even.

The product of its digits is 576, while the sum is 25.

The square root of 1661281 is about 1288.9069012151. The cubic root of 1661281 is about 118.4352640653.

The spelling of 1661281 in words is "one million, six hundred sixty-one thousand, two hundred eighty-one".