20857645 has 8 divisors (see below), whose sum is σ = 25210080. Its totient is φ = 16565520.

The previous prime is 20857631. The next prime is 20857663. The reversal of 20857645 is 54675802.

It is a happy number.

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

It is not a de Polignac number, because 20857645 - 2⁷ = 20857517 is a prime.

It is a super-3 number, since 3×20857645³ (a number of 23 digits) contains 333 as substring.

20857645 is a modest number, since divided by 7645 gives 2085 as remainder.

It is a congruent number.

It is an unprimeable number.

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 7 ways as a sum of consecutive naturals, for example, 14311 + ... + 15700.

It is an arithmetic number, because the mean of its divisors is an integer number (3151260).

Almost surely, 2^20857645 is an apocalyptic number.

It is an amenable number.

20857645 is a deficient number, since it is larger than the sum of its proper divisors (4352435).

20857645 is a wasteful number, since it uses less digits than its factorization.

20857645 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 30155.

The product of its (nonzero) digits is 67200, while the sum is 37.

The square root of 20857645 is about 4567.0170790134. The cubic root of 20857645 is about 275.2675962730.

It can be divided in two parts, 2085 and 7645, that added together give a triangular number (9730 = T₁₃₉).

The spelling of 20857645 in words is "twenty million, eight hundred fifty-seven thousand, six hundred forty-five".