21005153 has 4 divisors (see below), whose sum is σ = 22620948. Its totient is φ = 19389360.

The previous prime is 21005143. The next prime is 21005177. The reversal of 21005153 is 35150012.

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 9560464 + 11444689 = 3092^2 + 3383^2 .

It is a cyclic number.

It is not a de Polignac number, because 21005153 - 2⁸ = 21004897 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21005123) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 807878 + ... + 807903.

It is an arithmetic number, because the mean of its divisors is an integer number (5655237).

Almost surely, 2^21005153 is an apocalyptic number.

It is an amenable number.

21005153 is a deficient number, since it is larger than the sum of its proper divisors (1615795).

21005153 is a wasteful number, since it uses less digits than its factorization.

21005153 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1615794.

The product of its (nonzero) digits is 150, while the sum is 17.

The square root of 21005153 is about 4583.1378988636. The cubic root of 21005153 is about 275.9149820407.

Adding to 21005153 its reverse (35150012), we get a palindrome (56155165).

The spelling of 21005153 in words is "twenty-one million, five thousand, one hundred fifty-three".