21913645 has 16 divisors (see below), whose sum is σ = 28858032. Its totient is φ = 15874560.

The previous prime is 21913643. The next prime is 21913679. The reversal of 21913645 is 54631912.

It can be written as a sum of positive squares in 8 ways, for example, as 1726596 + 20187049 = 1314^2 + 4493^2 .

It is not a de Polignac number, because 21913645 - 2¹ = 21913643 is a prime.

It is a super-3 number, since 3×21913645³ (a number of 23 digits) contains 333 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 (21913643) 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 15 ways as a sum of consecutive naturals, for example, 265 + ... + 6625.

It is an arithmetic number, because the mean of its divisors is an integer number (1803627).

Almost surely, 2^21913645 is an apocalyptic number.

It is an amenable number.

21913645 is a deficient number, since it is larger than the sum of its proper divisors (6944387).

21913645 is a wasteful number, since it uses less digits than its factorization.

21913645 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6432.

The product of its digits is 6480, while the sum is 31.

The square root of 21913645 is about 4681.2012347260. The cubic root of 21913645 is about 279.8368309527.

The spelling of 21913645 in words is "twenty-one million, nine hundred thirteen thousand, six hundred forty-five".