2117721 has 16 divisors (see below), whose sum is σ = 3032640. Its totient is φ = 1310400.

The previous prime is 2117719. The next prime is 2117723. The reversal of 2117721 is 1277112.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (2117719) and next prime (2117723).

It is not a de Polignac number, because 2117721 - 2¹ = 2117719 is a prime.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (2117723) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 2671 + ... + 3371.

It is an arithmetic number, because the mean of its divisors is an integer number (189540).

2^2117721 is an apocalyptic number.

It is an amenable number.

2117721 is a deficient number, since it is larger than the sum of its proper divisors (914919).

2117721 is a wasteful number, since it uses less digits than its factorization.

2117721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 776.

The product of its digits is 196, while the sum is 21.

The square root of 2117721 is about 1455.2391556030. The cubic root of 2117721 is about 128.4171166320.

The spelling of 2117721 in words is "two million, one hundred seventeen thousand, seven hundred twenty-one".