21663426 has 16 divisors (see below), whose sum is σ = 44498304. Its totient is φ = 7025904.

The previous prime is 21663419. The next prime is 21663427. The reversal of 21663426 is 62436612.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 21663393 and 21663402.

It is not an unprimeable number, because it can be changed into a prime (21663427) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 48570 + ... + 49013.

It is an arithmetic number, because the mean of its divisors is an integer number (2781144).

Almost surely, 2^21663426 is an apocalyptic number.

21663426 is an abundant number, since it is smaller than the sum of its proper divisors (22834878).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21663426 is a wasteful number, since it uses less digits than its factorization.

21663426 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 97625.

The product of its digits is 10368, while the sum is 30.

The square root of 21663426 is about 4654.3985647987. The cubic root of 21663426 is about 278.7676538385.

The spelling of 21663426 in words is "twenty-one million, six hundred sixty-three thousand, four hundred twenty-six".