20100221 has 4 divisors (see below), whose sum is σ = 20567712. Its totient is φ = 19632732.

The previous prime is 20100217. The next prime is 20100251. The reversal of 20100221 is 12200102.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 12200102 = 2 ⋅6100051.

It is a cyclic number.

It is not a de Polignac number, because 20100221 - 2² = 20100217 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 20100199 and 20100208.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20100251) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 233681 + ... + 233766.

It is an arithmetic number, because the mean of its divisors is an integer number (5141928).

Almost surely, 2^20100221 is an apocalyptic number.

It is an amenable number.

20100221 is a deficient number, since it is larger than the sum of its proper divisors (467491).

20100221 is an equidigital number, since it uses as much as digits as its factorization.

20100221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 467490.

The product of its (nonzero) digits is 8, while the sum is 8.

The square root of 20100221 is about 4483.3270012347. The cubic root of 20100221 is about 271.8944091662.

Adding to 20100221 its reverse (12200102), we get a palindrome (32300323).

The spelling of 20100221 in words is "twenty million, one hundred thousand, two hundred twenty-one".