33721 has 2 divisors, whose sum is σ = 33722. Its totient is φ = 33720.

The previous prime is 33713. The next prime is 33739. The reversal of 33721 is 12733.

33721 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 19321 + 14400 = 139^2 + 120^2 .

It is a cyclic number.

It is not a de Polignac number, because 33721 - 2³ = 33713 is a prime.

It is a super-2 number, since 2×33721² = 2274211682, which contains 22 as substring.

It is an Ulam number.

33721 is a lucky number.

It is a plaindrome in base 13.

It is a junction number, because it is equal to n+sod(n) for n = 33695 and 33704.

It is not a weakly prime, because it can be changed into another prime (33751) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 16860 + 16861.

It is an arithmetic number, because the mean of its divisors is an integer number (16861).

2³³⁷²¹ is an apocalyptic number.

It is an amenable number.

33721 is a deficient number, since it is larger than the sum of its proper divisors (1).

33721 is an equidigital number, since it uses as much as digits as its factorization.

33721 is an evil number, because the sum of its binary digits is even.

The product of its digits is 126, while the sum is 16.

The square root of 33721 is about 183.6327857437. The cubic root of 33721 is about 32.3072616083.

The spelling of 33721 in words is "thirty-three thousand, seven hundred twenty-one".