20507221 has 4 divisors (see below), whose sum is σ = 23436832. Its totient is φ = 17577612.

The previous prime is 20507203. The next prime is 20507231. The reversal of 20507221 is 12270502.

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: 12270502 = 2 ⋅6135251.

It is a cyclic number.

It is not a de Polignac number, because 20507221 - 2¹⁵ = 20474453 is a prime.

It is a super-2 number, since 2×20507221² = 841092226285682, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20507231) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1464795 + ... + 1464808.

It is an arithmetic number, because the mean of its divisors is an integer number (5859208).

Almost surely, 2^20507221 is an apocalyptic number.

It is an amenable number.

20507221 is a deficient number, since it is larger than the sum of its proper divisors (2929611).

20507221 is an equidigital number, since it uses as much as digits as its factorization.

20507221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2929610.

The product of its (nonzero) digits is 280, while the sum is 19.

The square root of 20507221 is about 4528.4899249087. The cubic root of 20507221 is about 273.7173146133.

Adding to 20507221 its reverse (12270502), we get a palindrome (32777723).

The spelling of 20507221 in words is "twenty million, five hundred seven thousand, two hundred twenty-one".