20721045 has 32 divisors (see below), whose sum is σ = 36640512. Its totient is φ = 9946112.

The previous prime is 20721037. The next prime is 20721047. The reversal of 20721045 is 54012702.

It is a cyclic number.

It is not a de Polignac number, because 20721045 - 2³ = 20721037 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 (20721047) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 4099 + ... + 7631.

It is an arithmetic number, because the mean of its divisors is an integer number (1145016).

Almost surely, 2^20721045 is an apocalyptic number.

It is an amenable number.

20721045 is a deficient number, since it is larger than the sum of its proper divisors (15919467).

20721045 is a wasteful number, since it uses less digits than its factorization.

20721045 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3581.

The product of its (nonzero) digits is 560, while the sum is 21.

The square root of 20721045 is about 4552.0374559092. The cubic root of 20721045 is about 274.6653560266.

Adding to 20721045 its reverse (54012702), we get a palindrome (74733747).

The spelling of 20721045 in words is "twenty million, seven hundred twenty-one thousand, forty-five".