21821965 has 16 divisors (see below), whose sum is σ = 30248640. Its totient is φ = 14936320.

The previous prime is 21821953. The next prime is 21821977. The reversal of 21821965 is 56912812.

It is an interprime number because it is at equal distance from previous prime (21821953) and next prime (21821977).

It is not a de Polignac number, because 21821965 - 2¹⁵ = 21789197 is a prime.

It is a super-2 number, since 2×21821965² = 952396312922450, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 21821965.

It is a congruent number.

It is an unprimeable number.

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 15 ways as a sum of consecutive naturals, for example, 10735 + ... + 12604.

It is an arithmetic number, because the mean of its divisors is an integer number (1890540).

Almost surely, 2^21821965 is an apocalyptic number.

It is an amenable number.

21821965 is a deficient number, since it is larger than the sum of its proper divisors (8426675).

21821965 is a wasteful number, since it uses less digits than its factorization.

21821965 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 23372.

The product of its digits is 8640, while the sum is 34.

The square root of 21821965 is about 4671.3986128353. The cubic root of 21821965 is about 279.4460348341.

The spelling of 21821965 in words is "twenty-one million, eight hundred twenty-one thousand, nine hundred sixty-five".