20021945 has 16 divisors (see below), whose sum is σ = 24822720. Its totient is φ = 15495744.

The previous prime is 20021917. The next prime is 20021951. The reversal of 20021945 is 54912002.

It is a cyclic number.

It is not a de Polignac number, because 20021945 - 2⁸ = 20021689 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 20021945.

It is an unprimeable number.

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 15 ways as a sum of consecutive naturals, for example, 19259 + ... + 20271.

It is an arithmetic number, because the mean of its divisors is an integer number (1551420).

Almost surely, 2^20021945 is an apocalyptic number.

It is an amenable number.

20021945 is a deficient number, since it is larger than the sum of its proper divisors (4800775).

20021945 is a wasteful number, since it uses less digits than its factorization.

20021945 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1144.

The product of its (nonzero) digits is 720, while the sum is 23.

The square root of 20021945 is about 4474.5888079241. The cubic root of 20021945 is about 271.5410051943.

Adding to 20021945 its reverse (54912002), we get a palindrome (74933947).

The spelling of 20021945 in words is "twenty million, twenty-one thousand, nine hundred forty-five".