21013553 has 4 divisors (see below), whose sum is σ = 22923888. Its totient is φ = 19103220.

The previous prime is 21013549. The next prime is 21013583. The reversal of 21013553 is 35531012.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21013553 - 2² = 21013549 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21013543) 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, 955151 + ... + 955172.

It is an arithmetic number, because the mean of its divisors is an integer number (5730972).

Almost surely, 2^21013553 is an apocalyptic number.

It is an amenable number.

21013553 is a deficient number, since it is larger than the sum of its proper divisors (1910335).

21013553 is a wasteful number, since it uses less digits than its factorization.

21013553 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1910334.

The product of its (nonzero) digits is 450, while the sum is 20.

The square root of 21013553 is about 4584.0542099761. The cubic root of 21013553 is about 275.9517567782.

Adding to 21013553 its reverse (35531012), we get a palindrome (56544565).

The spelling of 21013553 in words is "twenty-one million, thirteen thousand, five hundred fifty-three".