20211557 has 4 divisors (see below), whose sum is σ = 20542956. Its totient is φ = 19880160.

The previous prime is 20211533. The next prime is 20211559. The reversal of 20211557 is 75511202.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 6713281 + 13498276 = 2591^2 + 3674^2 .

It is a cyclic number.

It is not a de Polignac number, because 20211557 - 2⁶ = 20211493 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 (20211559) 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, 165608 + ... + 165729.

It is an arithmetic number, because the mean of its divisors is an integer number (5135739).

Almost surely, 2^20211557 is an apocalyptic number.

It is an amenable number.

20211557 is a deficient number, since it is larger than the sum of its proper divisors (331399).

20211557 is an equidigital number, since it uses as much as digits as its factorization.

20211557 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 331398.

The product of its (nonzero) digits is 700, while the sum is 23.

The square root of 20211557 is about 4495.7265263804. The cubic root of 20211557 is about 272.3954967799.

Adding to 20211557 its reverse (75511202), we get a palindrome (95722759).

The spelling of 20211557 in words is "twenty million, two hundred eleven thousand, five hundred fifty-seven".