20870221 has 4 divisors (see below), whose sum is σ = 20969344. Its totient is φ = 20771100.

The previous prime is 20870219. The next prime is 20870231. The reversal of 20870221 is 12207802.

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.

It is a cyclic number.

It is not a de Polignac number, because 20870221 - 2¹ = 20870219 is a prime.

It is a super-2 number, since 2×20870221² = 871132249177682, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 20870192 and 20870201.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20870231) 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, 49245 + ... + 49666.

It is an arithmetic number, because the mean of its divisors is an integer number (5242336).

Almost surely, 2^20870221 is an apocalyptic number.

It is an amenable number.

20870221 is a deficient number, since it is larger than the sum of its proper divisors (99123).

20870221 is an equidigital number, since it uses as much as digits as its factorization.

20870221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 99122.

The product of its (nonzero) digits is 448, while the sum is 22.

The square root of 20870221 is about 4568.3937001970. The cubic root of 20870221 is about 275.3229088418.

The spelling of 20870221 in words is "twenty million, eight hundred seventy thousand, two hundred twenty-one".