20721171 has 8 divisors (see below), whose sum is σ = 27656640. Its totient is φ = 13799912.

The previous prime is 20721163. The next prime is 20721209. The reversal of 20721171 is 17112702.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 20721171 - 2³ = 20721163 is a prime.

It is a super-2 number, since 2×20721171² = 858733855222482, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (20721101) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 520 + ... + 6458.

It is an arithmetic number, because the mean of its divisors is an integer number (3457080).

Almost surely, 2^20721171 is an apocalyptic number.

20721171 is a deficient number, since it is larger than the sum of its proper divisors (6935469).

20721171 is a wasteful number, since it uses less digits than its factorization.

20721171 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7105.

The product of its (nonzero) digits is 196, while the sum is 21.

The square root of 20721171 is about 4552.0512958445. The cubic root of 20721171 is about 274.6659127515.

Adding to 20721171 its reverse (17112702), we get a palindrome (37833873).

The spelling of 20721171 in words is "twenty million, seven hundred twenty-one thousand, one hundred seventy-one".