1281721 has 16 divisors (see below), whose sum is σ = 1612800. Its totient is φ = 993168.

The previous prime is 1281703. The next prime is 1281727. The reversal of 1281721 is 1271821.

It is not a de Polignac number, because 1281721 - 2¹¹ = 1279673 is a prime.

1281721 is a lucky number.

It is a junction number, because it is equal to n+sod(n) for n = 1281692 and 1281701.

It is not an unprimeable number, because it can be changed into a prime (1281727) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 2850 + ... + 3268.

It is an arithmetic number, because the mean of its divisors is an integer number (100800).

2^1281721 is an apocalyptic number.

It is an amenable number.

1281721 is a deficient number, since it is larger than the sum of its proper divisors (331079).

1281721 is a wasteful number, since it uses less digits than its factorization.

1281721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 468.

The product of its digits is 224, while the sum is 22.

The square root of 1281721 is about 1132.1311761452. The cubic root of 1281721 is about 108.6253444619.

It can be divided in two parts, 1281 and 721, that added together give a palindrome (2002).

The spelling of 1281721 in words is "one million, two hundred eighty-one thousand, seven hundred twenty-one".