21353506 has 4 divisors (see below), whose sum is σ = 32030262. Its totient is φ = 10676752.

The previous prime is 21353491. The next prime is 21353531. The reversal of 21353506 is 60535312.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in only one way, i.e., 11799225 + 9554281 = 3435^2 + 3091^2 .

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5338375 + ... + 5338378.

Almost surely, 2^21353506 is an apocalyptic number.

21353506 is a deficient number, since it is larger than the sum of its proper divisors (10676756).

21353506 is a wasteful number, since it uses less digits than its factorization.

21353506 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10676755.

The product of its (nonzero) digits is 2700, while the sum is 25.

The square root of 21353506 is about 4620.9853927490. The cubic root of 21353506 is about 277.4319006123.

Adding to 21353506 its reverse (60535312), we get a palindrome (81888818).

The spelling of 21353506 in words is "twenty-one million, three hundred fifty-three thousand, five hundred six".