21536623 has 2 divisors, whose sum is σ = 21536624. Its totient is φ = 21536622.

The previous prime is 21536621. The next prime is 21536629. The reversal of 21536623 is 32663512.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21536623 - 2¹ = 21536621 is a prime.

It is a super-2 number, since 2×21536623² = 927652260488258, which contains 22 as substring.

Together with 21536621, it forms a pair of twin primes.

It is equal to p_1361737 and since 21536623 and 1361737 have the same sum of digits, it is a Honaker prime.

It is a junction number, because it is equal to n+sod(n) for n = 21536591 and 21536600.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21536621) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10768311 + 10768312.

It is an arithmetic number, because the mean of its divisors is an integer number (10768312).

Almost surely, 2^21536623 is an apocalyptic number.

21536623 is a deficient number, since it is larger than the sum of its proper divisors (1).

21536623 is an equidigital number, since it uses as much as digits as its factorization.

21536623 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 6480, while the sum is 28.

The square root of 21536623 is about 4640.7567270867. The cubic root of 21536623 is about 278.2226835765. Note that the first 3 decimals are identical.

The spelling of 21536623 in words is "twenty-one million, five hundred thirty-six thousand, six hundred twenty-three".