33005721 has 32 divisors (see below), whose sum is σ = 54190080. Its totient is φ = 17438976.

The previous prime is 33005701. The next prime is 33005729. The reversal of 33005721 is 12750033.

It is a happy number.

It is not a de Polignac number, because 33005721 - 2¹⁷ = 32874649 is a prime.

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

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (33005729) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 20280 + ... + 21846.

It is an arithmetic number, because the mean of its divisors is an integer number (1693440).

Almost surely, 2^33005721 is an apocalyptic number.

It is an amenable number.

33005721 is a deficient number, since it is larger than the sum of its proper divisors (21184359).

33005721 is a wasteful number, since it uses less digits than its factorization.

33005721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1653.

The product of its (nonzero) digits is 630, while the sum is 21.

The square root of 33005721 is about 5745.0605740932. The cubic root of 33005721 is about 320.7719675891.

Adding to 33005721 its reverse (12750033), we get a palindrome (45755754).

It can be divided in two parts, 330057 and 21, that added together give a triangular number (330078 = T₈₁₂).

The spelling of 33005721 in words is "thirty-three million, five thousand, seven hundred twenty-one".