21701623 has 2 divisors, whose sum is σ = 21701624. Its totient is φ = 21701622.

The previous prime is 21701621. The next prime is 21701651. The reversal of 21701623 is 32610712.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21701623 - 2¹ = 21701621 is a prime.

Together with 21701621, it forms a pair of twin primes.

It is the 4659-th Hogben number.

It is a junction number, because it is equal to n+sod(n) for n = 21701594 and 21701603.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21701621) by changing a digit.

It is a nontrivial repunit in base 4658.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10850811 + 10850812.

It is an arithmetic number, because the mean of its divisors is an integer number (10850812).

Almost surely, 2^21701623 is an apocalyptic number.

21701623 is a deficient number, since it is larger than the sum of its proper divisors (1).

21701623 is an equidigital number, since it uses as much as digits as its factorization.

21701623 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 504, while the sum is 22.

The square root of 21701623 is about 4658.5000804980. The cubic root of 21701623 is about 278.9313988828.

The spelling of 21701623 in words is "twenty-one million, seven hundred one thousand, six hundred twenty-three".