21012553 has 4 divisors (see below), whose sum is σ = 21209040. Its totient is φ = 20816068.

The previous prime is 21012533. The next prime is 21012569. The reversal of 21012553 is 35521012.

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 a de Polignac number, because none of the positive numbers 2^k-21012553 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21012553.

It is not an unprimeable number, because it can be changed into a prime (21012503) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 98083 + ... + 98296.

It is an arithmetic number, because the mean of its divisors is an integer number (5302260).

Almost surely, 2^21012553 is an apocalyptic number.

It is an amenable number.

21012553 is a deficient number, since it is larger than the sum of its proper divisors (196487).

21012553 is a wasteful number, since it uses less digits than its factorization.

21012553 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 196486.

The product of its (nonzero) digits is 300, while the sum is 19.

The square root of 21012553 is about 4583.9451349247. The cubic root of 21012553 is about 275.9473793473.

Adding to 21012553 its reverse (35521012), we get a palindrome (56533565).

The spelling of 21012553 in words is "twenty-one million, twelve thousand, five hundred fifty-three".