20857381 has 8 divisors (see below), whose sum is σ = 21501464. Its totient is φ = 20217600.

The previous prime is 20857373. The next prime is 20857387. The reversal of 20857381 is 18375802.

It can be written as a sum of positive squares in 4 ways, for example, as 72900 + 20784481 = 270^2 + 4559^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 20857381 - 2³ = 20857373 is a prime.

It is a super-2 number, since 2×20857381² = 870060684358322, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20857387) 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 7 ways as a sum of consecutive naturals, for example, 10681 + ... + 12481.

It is an arithmetic number, because the mean of its divisors is an integer number (2687683).

Almost surely, 2^20857381 is an apocalyptic number.

It is an amenable number.

20857381 is a deficient number, since it is larger than the sum of its proper divisors (644083).

20857381 is a wasteful number, since it uses less digits than its factorization.

20857381 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2151.

The product of its (nonzero) digits is 13440, while the sum is 34.

The square root of 20857381 is about 4566.9881760302. The cubic root of 20857381 is about 275.2664348930.

The spelling of 20857381 in words is "twenty million, eight hundred fifty-seven thousand, three hundred eighty-one".