21039553 has 4 divisors (see below), whose sum is σ = 21053488. Its totient is φ = 21025620.

The previous prime is 21039527. The next prime is 21039559. The reversal of 21039553 is 35593012.

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 21039553 - 2⁵ = 21039521 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21039559) 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, 4383 + ... + 7828.

It is an arithmetic number, because the mean of its divisors is an integer number (5263372).

Almost surely, 2^21039553 is an apocalyptic number.

It is an amenable number.

21039553 is a deficient number, since it is larger than the sum of its proper divisors (13935).

21039553 is a wasteful number, since it uses less digits than its factorization.

21039553 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 13934.

The product of its (nonzero) digits is 4050, while the sum is 28.

The square root of 21039553 is about 4586.8892508976. The cubic root of 21039553 is about 276.0655212713.

The spelling of 21039553 in words is "twenty-one million, thirty-nine thousand, five hundred fifty-three".