20918057 has 4 divisors (see below), whose sum is σ = 20940036. Its totient is φ = 20896080.

The previous prime is 20918047. The next prime is 20918071. The reversal of 20918057 is 75081902.

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 14622976 + 6295081 = 3824^2 + 2509^2 .

It is a cyclic number.

It is not a de Polignac number, because 20918057 - 2¹⁶ = 20852521 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20918047) 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, 9494 + ... + 11487.

It is an arithmetic number, because the mean of its divisors is an integer number (5235009).

Almost surely, 2^20918057 is an apocalyptic number.

It is an amenable number.

20918057 is a deficient number, since it is larger than the sum of its proper divisors (21979).

20918057 is an equidigital number, since it uses as much as digits as its factorization.

20918057 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 21978.

The product of its (nonzero) digits is 5040, while the sum is 32.

The square root of 20918057 is about 4573.6262418348. The cubic root of 20918057 is about 275.5331014253.

Adding to 20918057 its reverse (75081902), we get a palindrome (95999959).

The spelling of 20918057 in words is "twenty million, nine hundred eighteen thousand, fifty-seven".