20615221 has 4 divisors (see below), whose sum is σ = 22489344. Its totient is φ = 18741100.

The previous prime is 20615213. The next prime is 20615233. The reversal of 20615221 is 12251602.

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 20615221 - 2³ = 20615213 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20615261) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 937045 + ... + 937066.

It is an arithmetic number, because the mean of its divisors is an integer number (5622336).

Almost surely, 2^20615221 is an apocalyptic number.

It is an amenable number.

20615221 is a deficient number, since it is larger than the sum of its proper divisors (1874123).

20615221 is a wasteful number, since it uses less digits than its factorization.

20615221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1874122.

The product of its (nonzero) digits is 240, while the sum is 19.

The square root of 20615221 is about 4540.3987710332. The cubic root of 20615221 is about 274.1969786096.

Adding to 20615221 its reverse (12251602), we get a palindrome (32866823).

The spelling of 20615221 in words is "twenty million, six hundred fifteen thousand, two hundred twenty-one".