21633361 has 4 divisors (see below), whose sum is σ = 21643072. Its totient is φ = 21623652.

The previous prime is 21633349. The next prime is 21633371. The reversal of 21633361 is 16333612.

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, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 21633361 - 2⁵ = 21633329 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21633371) 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, 340 + ... + 6586.

It is an arithmetic number, because the mean of its divisors is an integer number (5410768).

Almost surely, 2^21633361 is an apocalyptic number.

It is an amenable number.

21633361 is a deficient number, since it is larger than the sum of its proper divisors (9711).

21633361 is an equidigital number, since it uses as much as digits as its factorization.

21633361 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9710.

The product of its digits is 1944, while the sum is 25.

The square root of 21633361 is about 4651.1677028462. The cubic root of 21633361 is about 278.6386340843.

Adding to 21633361 its reverse (16333612), we get a palindrome (37966973).

The spelling of 21633361 in words is "twenty-one million, six hundred thirty-three thousand, three hundred sixty-one".