2261721 has 16 divisors (see below), whose sum is σ = 3760128. Its totient is φ = 1174800.

The previous prime is 2261717. The next prime is 2261737. The reversal of 2261721 is 1271622.

It is not a de Polignac number, because 2261721 - 2² = 2261717 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (21).

It is a Curzon number.

2261721 is a lucky number.

It is not an unprimeable number, because it can be changed into a prime (2261771) 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, 4665 + ... + 5126.

It is an arithmetic number, because the mean of its divisors is an integer number (235008).

2^2261721 is an apocalyptic number.

2261721 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

2261721 is a deficient number, since it is larger than the sum of its proper divisors (1498407).

2261721 is a wasteful number, since it uses less digits than its factorization.

2261721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9812.

The product of its digits is 336, while the sum is 21.

The square root of 2261721 is about 1503.9019249938. The cubic root of 2261721 is about 131.2642143336.

2261721 divided by its sum of digits (21) gives a palindrome (107701).

Subtracting from 2261721 its reverse (1271622), we obtain a palindrome (990099).

The spelling of 2261721 in words is "two million, two hundred sixty-one thousand, seven hundred twenty-one".