21312233 has 2 divisors, whose sum is σ = 21312234. Its totient is φ = 21312232.

The previous prime is 21312229. The next prime is 21312257. The reversal of 21312233 is 33221312.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 11377129 + 9935104 = 3373^2 + 3152^2 .

It is a cyclic number.

It is not a de Polignac number, because 21312233 - 2² = 21312229 is a prime.

It is a super-2 number, since 2×21312233² = 908422550892578, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21312223) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10656116 + 10656117.

It is an arithmetic number, because the mean of its divisors is an integer number (10656117).

Almost surely, 2^21312233 is an apocalyptic number.

It is an amenable number.

21312233 is a deficient number, since it is larger than the sum of its proper divisors (1).

21312233 is an equidigital number, since it uses as much as digits as its factorization.

21312233 is an evil number, because the sum of its binary digits is even.

The product of its digits is 216, while the sum is 17.

The square root of 21312233 is about 4616.5174103430. The cubic root of 21312233 is about 277.2530411145.

Adding to 21312233 its reverse (33221312), we get a palindrome (54533545).

The spelling of 21312233 in words is "twenty-one million, three hundred twelve thousand, two hundred thirty-three".