21916945 has 4 divisors (see below), whose sum is σ = 26300340. Its totient is φ = 17533552.

The previous prime is 21916901. The next prime is 21916967. The reversal of 21916945 is 54961912.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 7568001 + 14348944 = 2751^2 + 3788^2 .

It is a cyclic number.

It is not a de Polignac number, because 21916945 - 2¹³ = 21908753 is a prime.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2191690 + ... + 2191699.

It is an arithmetic number, because the mean of its divisors is an integer number (6575085).

Almost surely, 2^21916945 is an apocalyptic number.

It is an amenable number.

21916945 is a deficient number, since it is larger than the sum of its proper divisors (4383395).

21916945 is an equidigital number, since it uses as much as digits as its factorization.

21916945 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4383394.

The product of its digits is 19440, while the sum is 37.

The square root of 21916945 is about 4681.5536950888. The cubic root of 21916945 is about 279.8508772267.

The spelling of 21916945 in words is "twenty-one million, nine hundred sixteen thousand, nine hundred forty-five".