21969845 has 4 divisors (see below), whose sum is σ = 26363820. Its totient is φ = 17575872.

The previous prime is 21969817. The next prime is 21969847. The reversal of 21969845 is 54896912.

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 15928081 + 6041764 = 3991^2 + 2458^2 .

It is a cyclic number.

It is not a de Polignac number, because 21969845 - 2⁶ = 21969781 is a prime.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 21969796 and 21969805.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21969847) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2196980 + ... + 2196989.

It is an arithmetic number, because the mean of its divisors is an integer number (6590955).

Almost surely, 2^21969845 is an apocalyptic number.

It is an amenable number.

21969845 is a deficient number, since it is larger than the sum of its proper divisors (4393975).

21969845 is an equidigital number, since it uses as much as digits as its factorization.

21969845 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4393974.

The product of its digits is 155520, while the sum is 44.

The square root of 21969845 is about 4687.2001237413. The cubic root of 21969845 is about 280.0758510490.

The spelling of 21969845 in words is "twenty-one million, nine hundred sixty-nine thousand, eight hundred forty-five".