21969785 has 4 divisors (see below), whose sum is σ = 26363748. Its totient is φ = 17575824.

The previous prime is 21969781. The next prime is 21969811. The reversal of 21969785 is 58796912.

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 7139584 + 14830201 = 2672^2 + 3851^2 .

It is a cyclic number.

It is not a de Polignac number, because 21969785 - 2² = 21969781 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21969781) 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, 2196974 + ... + 2196983.

It is an arithmetic number, because the mean of its divisors is an integer number (6590937).

Almost surely, 2^21969785 is an apocalyptic number.

It is an amenable number.

21969785 is a deficient number, since it is larger than the sum of its proper divisors (4393963).

21969785 is an equidigital number, since it uses as much as digits as its factorization.

21969785 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4393962.

The product of its digits is 272160, while the sum is 47.

The square root of 21969785 is about 4687.1937233274. The cubic root of 21969785 is about 280.0755960849.

The spelling of 21969785 in words is "twenty-one million, nine hundred sixty-nine thousand, seven hundred eighty-five".