21235645 has 4 divisors (see below), whose sum is σ = 25482780. Its totient is φ = 16988512.

The previous prime is 21235639. The next prime is 21235657. The reversal of 21235645 is 54653212.

21235645 = 3258² + 3259².

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 10614564 + 10621081 = 3258^2 + 3259^2 .

It is a cyclic number.

It is not a de Polignac number, because 21235645 - 2⁷ = 21235517 is a prime.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2123560 + ... + 2123569.

It is an arithmetic number, because the mean of its divisors is an integer number (6370695).

Almost surely, 2^21235645 is an apocalyptic number.

21235645 is the 3259-th centered square number.

It is an amenable number.

21235645 is a deficient number, since it is larger than the sum of its proper divisors (4247135).

21235645 is an equidigital number, since it uses as much as digits as its factorization.

21235645 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4247134.

The product of its digits is 7200, while the sum is 28.

The square root of 21235645 is about 4608.2149472437. The cubic root of 21235645 is about 276.9205287535.

Adding to 21235645 its reverse (54653212), we get a palindrome (75888857).

The spelling of 21235645 in words is "twenty-one million, two hundred thirty-five thousand, six hundred forty-five".