20715857 has 4 divisors (see below), whose sum is σ = 20768436. Its totient is φ = 20663280.

The previous prime is 20715853. The next prime is 20715899. The reversal of 20715857 is 75851702.

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 7349521 + 13366336 = 2711^2 + 3656^2 .

It is a cyclic number.

It is not a de Polignac number, because 20715857 - 2² = 20715853 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20715853) 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, 25694 + ... + 26487.

It is an arithmetic number, because the mean of its divisors is an integer number (5192109).

Almost surely, 2^20715857 is an apocalyptic number.

It is an amenable number.

20715857 is a deficient number, since it is larger than the sum of its proper divisors (52579).

20715857 is an equidigital number, since it uses as much as digits as its factorization.

20715857 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 52578.

The product of its (nonzero) digits is 19600, while the sum is 35.

The square root of 20715857 is about 4551.4675655221. The cubic root of 20715857 is about 274.6424311402.

The spelling of 20715857 in words is "twenty million, seven hundred fifteen thousand, eight hundred fifty-seven".