21623603 has 2 divisors, whose sum is σ = 21623604. Its totient is φ = 21623602.

The previous prime is 21623599. The next prime is 21623617. The reversal of 21623603 is 30632612.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21623603 - 2² = 21623599 is a prime.

It is not a weakly prime, because it can be changed into another prime (21623633) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10811801 + 10811802.

It is an arithmetic number, because the mean of its divisors is an integer number (10811802).

Almost surely, 2^21623603 is an apocalyptic number.

21623603 is a deficient number, since it is larger than the sum of its proper divisors (1).

21623603 is an equidigital number, since it uses as much as digits as its factorization.

21623603 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1296, while the sum is 23.

The square root of 21623603 is about 4650.1186006381. The cubic root of 21623603 is about 278.5967332951.

Subtracting 21623603 from its reverse (30632612), we obtain a palindrome (9009009).

The spelling of 21623603 in words is "twenty-one million, six hundred twenty-three thousand, six hundred three".