20557531 has 4 divisors (see below), whose sum is σ = 20592792. Its totient is φ = 20522272.

The previous prime is 20557507. The next prime is 20557571. The reversal of 20557531 is 13575502.

20557531 is nontrivially palindromic in base 15.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 13575502 = 2 ⋅6787751.

It is a cyclic number.

It is not a de Polignac number, because 20557531 - 2¹³ = 20549339 is a prime.

It is a super-2 number, since 2×20557531² = 845224161631922, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 20557531.

It is not an unprimeable number, because it can be changed into a prime (20557571) 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, 16741 + ... + 17926.

It is an arithmetic number, because the mean of its divisors is an integer number (5148198).

Almost surely, 2^20557531 is an apocalyptic number.

20557531 is a deficient number, since it is larger than the sum of its proper divisors (35261).

20557531 is an equidigital number, since it uses as much as digits as its factorization.

20557531 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 35260.

The product of its (nonzero) digits is 5250, while the sum is 28.

The square root of 20557531 is about 4534.0413540240. The cubic root of 20557531 is about 273.9409670895.

The spelling of 20557531 in words is "twenty million, five hundred fifty-seven thousand, five hundred thirty-one".