20170221 has 8 divisors (see below), whose sum is σ = 26932800. Its totient is φ = 13427232.

The previous prime is 20170219. The next prime is 20170223. The reversal of 20170221 is 12207102.

It is an interprime number because it is at equal distance from previous prime (20170219) and next prime (20170223).

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

It is not a de Polignac number, because 20170221 - 2¹ = 20170219 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 20170221.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20170223) 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, 2296 + ... + 6753.

It is an arithmetic number, because the mean of its divisors is an integer number (3366600).

Almost surely, 2^20170221 is an apocalyptic number.

It is an amenable number.

20170221 is a deficient number, since it is larger than the sum of its proper divisors (6762579).

20170221 is an equidigital number, since it uses as much as digits as its factorization.

20170221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9795.

The product of its (nonzero) digits is 56, while the sum is 15.

The square root of 20170221 is about 4491.1269187143. The cubic root of 20170221 is about 272.2096719899.

Adding to 20170221 its reverse (12207102), we get a palindrome (32377323).

The spelling of 20170221 in words is "twenty million, one hundred seventy thousand, two hundred twenty-one".