21779945 has 16 divisors (see below), whose sum is σ = 28607040. Its totient is φ = 15787200.

The previous prime is 21779917. The next prime is 21779971. The reversal of 21779945 is 54997712.

It is not a de Polignac number, because 21779945 - 2⁶ = 21779881 is a prime.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 21779896 and 21779905.

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, 24926 + ... + 25784.

It is an arithmetic number, because the mean of its divisors is an integer number (1787940).

Almost surely, 2^21779945 is an apocalyptic number.

It is an amenable number.

21779945 is a deficient number, since it is larger than the sum of its proper divisors (6827095).

21779945 is a wasteful number, since it uses less digits than its factorization.

21779945 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1336.

The product of its digits is 158760, while the sum is 44.

The square root of 21779945 is about 4666.8988632710. The cubic root of 21779945 is about 279.2665540923.

The spelling of 21779945 in words is "twenty-one million, seven hundred seventy-nine thousand, nine hundred forty-five".