21645669 has 4 divisors (see below), whose sum is σ = 28860896. Its totient is φ = 14430444.

The previous prime is 21645619. The next prime is 21645683. The reversal of 21645669 is 96654612.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 21645669 - 2⁸ = 21645413 is a prime.

It is a super-2 number, since 2×21645669² = 937069972915122, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21645619) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3607609 + ... + 3607614.

It is an arithmetic number, because the mean of its divisors is an integer number (7215224).

Almost surely, 2^21645669 is an apocalyptic number.

It is an amenable number.

21645669 is a deficient number, since it is larger than the sum of its proper divisors (7215227).

21645669 is an equidigital number, since it uses as much as digits as its factorization.

21645669 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7215226.

The product of its digits is 77760, while the sum is 39.

The square root of 21645669 is about 4652.4906233113. The cubic root of 21645669 is about 278.6914665919.

The spelling of 21645669 in words is "twenty-one million, six hundred forty-five thousand, six hundred sixty-nine".