21223257 has 8 divisors (see below), whose sum is σ = 30870240. Its totient is φ = 12862560.

The previous prime is 21223219. The next prime is 21223261. The reversal of 21223257 is 75232212.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21223257 - 2⁶ = 21223193 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21223277) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 321532 + ... + 321597.

It is an arithmetic number, because the mean of its divisors is an integer number (3858780).

Almost surely, 2^21223257 is an apocalyptic number.

It is an amenable number.

21223257 is a deficient number, since it is larger than the sum of its proper divisors (9646983).

21223257 is a wasteful number, since it uses less digits than its factorization.

21223257 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 643143.

The product of its digits is 1680, while the sum is 24.

The square root of 21223257 is about 4606.8706298311. The cubic root of 21223257 is about 276.8666702717.

Adding to 21223257 its reverse (75232212), we get a palindrome (96455469).

The spelling of 21223257 in words is "twenty-one million, two hundred twenty-three thousand, two hundred fifty-seven".