1661293281 has 4 divisors (see below), whose sum is σ = 2215057712. Its totient is φ = 1107528852.

The previous prime is 1661293273. The next prime is 1661293351. The reversal of 1661293281 is 1823921661.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 1823921661 = 3 ⋅607973887.

It is not a de Polignac number, because 1661293281 - 2³ = 1661293273 is a prime.

It is a super-2 number, since 2×1661293281² = 5519790730991489922, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1661293201) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 276882211 + ... + 276882216.

It is an arithmetic number, because the mean of its divisors is an integer number (553764428).

Almost surely, 2^1661293281 is an apocalyptic number.

It is an amenable number.

1661293281 is a deficient number, since it is larger than the sum of its proper divisors (553764431).

1661293281 is an equidigital number, since it uses as much as digits as its factorization.

1661293281 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 553764430.

The product of its digits is 31104, while the sum is 39.

The square root of 1661293281 is about 40758.9656517434. The cubic root of 1661293281 is about 1184.3555590834.

The spelling of 1661293281 in words is "one billion, six hundred sixty-one million, two hundred ninety-three thousand, two hundred eighty-one".