20543665 has 8 divisors (see below), whose sum is σ = 25253928. Its totient is φ = 16033920.

The previous prime is 20543657. The next prime is 20543671. The reversal of 20543665 is 56634502.

It can be written as a sum of positive squares in 4 ways, for example, as 1192464 + 19351201 = 1092^2 + 4399^2 .

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

It is not a de Polignac number, because 20543665 - 2³ = 20543657 is a prime.

It is a Duffinian 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, 49902 + ... + 50311.

It is an arithmetic number, because the mean of its divisors is an integer number (3156741).

Almost surely, 2^20543665 is an apocalyptic number.

It is an amenable number.

20543665 is a deficient number, since it is larger than the sum of its proper divisors (4710263).

20543665 is a wasteful number, since it uses less digits than its factorization.

20543665 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 100259.

The product of its (nonzero) digits is 21600, while the sum is 31.

The square root of 20543665 is about 4532.5119966747. The cubic root of 20543665 is about 273.8793624187.

The spelling of 20543665 in words is "twenty million, five hundred forty-three thousand, six hundred sixty-five".