21523401 has 20 divisors (see below), whose sum is σ = 32941524. Its totient is φ = 13996800.

The previous prime is 21523399. The next prime is 21523417. The reversal of 21523401 is 10432512.

It can be written as a sum of positive squares in 2 ways, for example, as 10732176 + 10791225 = 3276^2 + 3285^2 .

It is not a de Polignac number, because 21523401 - 2¹ = 21523399 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21523421) 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, 81 + ... + 6561.

Almost surely, 2^21523401 is an apocalyptic number.

It is an amenable number.

21523401 is a deficient number, since it is larger than the sum of its proper divisors (11418123).

21523401 is an equidigital number, since it uses as much as digits as its factorization.

21523401 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6534 (or 6525 counting only the distinct ones).

The product of its (nonzero) digits is 240, while the sum is 18.

The square root of 21523401 is about 4639.3319562196. The cubic root of 21523401 is about 278.1657354129.

Adding to 21523401 its reverse (10432512), we get a palindrome (31955913).

The spelling of 21523401 in words is "twenty-one million, five hundred twenty-three thousand, four hundred one".