21223917 has 64 divisors (see below), whose sum is σ = 38707200. Its totient is φ = 11309760.

The previous prime is 21223901. The next prime is 21223927. The reversal of 21223917 is 71932212.

It is not a de Polignac number, because 21223917 - 2⁴ = 21223901 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21223927) by changing a digit.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 88684 + ... + 88922.

It is an arithmetic number, because the mean of its divisors is an integer number (604800).

Almost surely, 2^21223917 is an apocalyptic number.

21223917 is a gapful number since it is divisible by the number (27) formed by its first and last digit.

It is an amenable number.

21223917 is a deficient number, since it is larger than the sum of its proper divisors (17483283).

21223917 is a wasteful number, since it uses less digits than its factorization.

21223917 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 295 (or 289 counting only the distinct ones).

The product of its digits is 1512, while the sum is 27.

The square root of 21223917 is about 4606.9422614137. The cubic root of 21223917 is about 276.8695402382.

It can be divided in two parts, 212239 and 17, that multiplied together give a palindrome (3608063).

The spelling of 21223917 in words is "twenty-one million, two hundred twenty-three thousand, nine hundred seventeen".