21919945 has 16 divisors (see below), whose sum is σ = 27436032. Its totient is φ = 16793280.

The previous prime is 21919927. The next prime is 21919951. The reversal of 21919945 is 54991912.

It is not a de Polignac number, because 21919945 - 2⁹ = 21919433 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21919898 and 21919907.

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 15 ways as a sum of consecutive naturals, for example, 15279 + ... + 16651.

It is an arithmetic number, because the mean of its divisors is an integer number (1714752).

Almost surely, 2^21919945 is an apocalyptic number.

It is an amenable number.

21919945 is a deficient number, since it is larger than the sum of its proper divisors (5516087).

21919945 is a wasteful number, since it uses less digits than its factorization.

21919945 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1512.

The product of its digits is 29160, while the sum is 40.

The square root of 21919945 is about 4681.8740905753. The cubic root of 21919945 is about 279.8636453434.

It can be divided in two parts, 219 and 19945, that added together give a square (20164 = 142²).

The spelling of 21919945 in words is "twenty-one million, nine hundred nineteen thousand, nine hundred forty-five".