21443623 has 2 divisors, whose sum is σ = 21443624. Its totient is φ = 21443622.

The previous prime is 21443621. The next prime is 21443629. The reversal of 21443623 is 32634412.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21443623 - 2¹ = 21443621 is a prime.

It is a super-2 number, since 2×21443623² = 919657934732258, which contains 22 as substring.

Together with 21443621, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21443621) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10721811 + 10721812.

It is an arithmetic number, because the mean of its divisors is an integer number (10721812).

Almost surely, 2^21443623 is an apocalyptic number.

21443623 is a deficient number, since it is larger than the sum of its proper divisors (1).

21443623 is an equidigital number, since it uses as much as digits as its factorization.

21443623 is an evil number, because the sum of its binary digits is even.

The product of its digits is 3456, while the sum is 25.

The square root of 21443623 is about 4630.7259690031. The cubic root of 21443623 is about 277.8216296221.

The spelling of 21443623 in words is "twenty-one million, four hundred forty-three thousand, six hundred twenty-three".