21435921 has 20 divisors (see below), whose sum is σ = 34486452. Its totient is φ = 13190688.

The previous prime is 21435919. The next prime is 21435941. The reversal of 21435921 is 12953412.

It can be written as a sum of positive squares in 2 ways, for example, as 7485696 + 13950225 = 2736^2 + 3735^2 .

It is not a de Polignac number, because 21435921 - 2¹ = 21435919 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is not an unprimeable number, because it can be changed into a prime (21435941) by changing a digit.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 9126 + ... + 11231.

Almost surely, 2^21435921 is an apocalyptic number.

It is an amenable number.

21435921 is a deficient number, since it is larger than the sum of its proper divisors (13050531).

21435921 is a wasteful number, since it uses less digits than its factorization.

21435921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 20382 (or 20373 counting only the distinct ones).

The product of its digits is 2160, while the sum is 27.

The square root of 21435921 is about 4629.8942752508. The cubic root of 21435921 is about 277.7883635018.

The spelling of 21435921 in words is "twenty-one million, four hundred thirty-five thousand, nine hundred twenty-one".