21033505 has 16 divisors (see below), whose sum is σ = 26838864. Its totient is φ = 15769600.

The previous prime is 21033479. The next prime is 21033517. The reversal of 21033505 is 50533012.

It can be written as a sum of positive squares in 8 ways, for example, as 1115136 + 19918369 = 1056^2 + 4463^2 .

It is not a de Polignac number, because 21033505 - 2⁹ = 21032993 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 29655 + ... + 30355.

It is an arithmetic number, because the mean of its divisors is an integer number (1677429).

Almost surely, 2^21033505 is an apocalyptic number.

It is an amenable number.

21033505 is a deficient number, since it is larger than the sum of its proper divisors (5805359).

21033505 is a wasteful number, since it uses less digits than its factorization.

21033505 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1076.

The product of its (nonzero) digits is 450, while the sum is 19.

The square root of 21033505 is about 4586.2299331804. The cubic root of 21033505 is about 276.0390662688.

Adding to 21033505 its reverse (50533012), we get a palindrome (71566517).

The spelling of 21033505 in words is "twenty-one million, thirty-three thousand, five hundred five".