21630233 has 4 divisors (see below), whose sum is σ = 21657780. Its totient is φ = 21602688.

The previous prime is 21630229. The next prime is 21630251. The reversal of 21630233 is 33203612.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 16999129 + 4631104 = 4123^2 + 2152^2 .

It is a cyclic number.

It is not a de Polignac number, because 21630233 - 2² = 21630229 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21630223) 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, 12560 + ... + 14177.

It is an arithmetic number, because the mean of its divisors is an integer number (5414445).

Almost surely, 2^21630233 is an apocalyptic number.

It is an amenable number.

21630233 is a deficient number, since it is larger than the sum of its proper divisors (27547).

21630233 is an equidigital number, since it uses as much as digits as its factorization.

21630233 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 27546.

The product of its (nonzero) digits is 648, while the sum is 20.

The square root of 21630233 is about 4650.8314310454. The cubic root of 21630233 is about 278.6252038448.

Adding to 21630233 its reverse (33203612), we get a palindrome (54833845).

The spelling of 21630233 in words is "twenty-one million, six hundred thirty thousand, two hundred thirty-three".