20721085 has 32 divisors (see below), whose sum is σ = 31352832. Its totient is φ = 12770880.

The previous prime is 20721083. The next prime is 20721089. The reversal of 20721085 is 58012702.

It is not a de Polignac number, because 20721085 - 2¹ = 20721083 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20721083) 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, 40944 + ... + 41446.

It is an arithmetic number, because the mean of its divisors is an integer number (979776).

Almost surely, 2^20721085 is an apocalyptic number.

It is an amenable number.

20721085 is a deficient number, since it is larger than the sum of its proper divisors (10631747).

20721085 is a wasteful number, since it uses less digits than its factorization.

20721085 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 633.

The product of its (nonzero) digits is 1120, while the sum is 25.

The square root of 20721085 is about 4552.0418495440. The cubic root of 20721085 is about 274.6655327649.

Adding to 20721085 its reverse (58012702), we get a palindrome (78733787).

The spelling of 20721085 in words is "twenty million, seven hundred twenty-one thousand, eighty-five".