1721663281 has 4 divisors (see below), whose sum is σ = 1854098932. Its totient is φ = 1589227632.

The previous prime is 1721663269. The next prime is 1721663291. The reversal of 1721663281 is 1823661271.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 1823661271 = 1319 ⋅1382609.

It can be written as a sum of positive squares in 2 ways, for example, as 722534400 + 999128881 = 26880^2 + 31609^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1721663281 is a prime.

It is a super-2 number, since 2×1721663281² = 5928248906287369922, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 1721663281.

It is not an unprimeable number, because it can be changed into a prime (1721663291) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 66217806 + ... + 66217831.

It is an arithmetic number, because the mean of its divisors is an integer number (463524733).

Almost surely, 2^1721663281 is an apocalyptic number.

It is an amenable number.

1721663281 is a deficient number, since it is larger than the sum of its proper divisors (132435651).

1721663281 is a wasteful number, since it uses less digits than its factorization.

1721663281 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 132435650.

The product of its digits is 24192, while the sum is 37.

The square root of 1721663281 is about 41492.9304942420. The cubic root of 1721663281 is about 1198.5313702369.

The spelling of 1721663281 in words is "one billion, seven hundred twenty-one million, six hundred sixty-three thousand, two hundred eighty-one".