21221533 has 16 divisors (see below), whose sum is σ = 22752000. Its totient is φ = 19760832.

The previous prime is 21221531. The next prime is 21221539. The reversal of 21221533 is 33512212.

It is not a de Polignac number, because 21221533 - 2¹ = 21221531 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21221533.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21221531) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 135091 + ... + 135247.

It is an arithmetic number, because the mean of its divisors is an integer number (1422000).

Almost surely, 2^21221533 is an apocalyptic number.

It is an amenable number.

21221533 is a deficient number, since it is larger than the sum of its proper divisors (1530467).

21221533 is a wasteful number, since it uses less digits than its factorization.

21221533 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 324.

The product of its digits is 360, while the sum is 19.

The square root of 21221533 is about 4606.6835141998. The cubic root of 21221533 is about 276.8591732907.

Adding to 21221533 its reverse (33512212), we get a palindrome (54733745).

It can be divided in two parts, 2122 and 1533, that added together give a triangular number (3655 = T₈₅).

The spelling of 21221533 in words is "twenty-one million, two hundred twenty-one thousand, five hundred thirty-three".