21969939 has 4 divisors (see below), whose sum is σ = 29293256. Its totient is φ = 14646624.

The previous prime is 21969919. The next prime is 21969977. The reversal of 21969939 is 93996912.

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

It is not a de Polignac number, because 21969939 - 2⁷ = 21969811 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21969919) by changing a digit.

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 3 ways as a sum of consecutive naturals, for example, 3661654 + ... + 3661659.

It is an arithmetic number, because the mean of its divisors is an integer number (7323314).

Almost surely, 2^21969939 is an apocalyptic number.

21969939 is a deficient number, since it is larger than the sum of its proper divisors (7323317).

21969939 is an equidigital number, since it uses as much as digits as its factorization.

21969939 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7323316.

The product of its digits is 236196, while the sum is 48.

The square root of 21969939 is about 4687.2101510387. The cubic root of 21969939 is about 280.0762504918.

The spelling of 21969939 in words is "twenty-one million, nine hundred sixty-nine thousand, nine hundred thirty-nine".