20721172 has 24 divisors (see below), whose sum is σ = 38989440. Its totient is φ = 9604800.

The previous prime is 20721163. The next prime is 20721209. The reversal of 20721172 is 27112702.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 672 + ... + 6472.

It is an arithmetic number, because the mean of its divisors is an integer number (1624560).

Almost surely, 2^20721172 is an apocalyptic number.

It is an amenable number.

20721172 is a deficient number, since it is larger than the sum of its proper divisors (18268268).

20721172 is a wasteful number, since it uses less digits than its factorization.

20721172 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5871 (or 5869 counting only the distinct ones).

The product of its (nonzero) digits is 392, while the sum is 22.

The square root of 20721172 is about 4552.0514056851. The cubic root of 20721172 is about 274.6659171700.

Adding to 20721172 its reverse (27112702), we get a palindrome (47833874).

The spelling of 20721172 in words is "twenty million, seven hundred twenty-one thousand, one hundred seventy-two".