21503423 has 2 divisors, whose sum is σ = 21503424. Its totient is φ = 21503422.

The previous prime is 21503399. The next prime is 21503437. The reversal of 21503423 is 32430512.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21503423 - 2⁶ = 21503359 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21503395 and 21503404.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21583423) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10751711 + 10751712.

It is an arithmetic number, because the mean of its divisors is an integer number (10751712).

Almost surely, 2^21503423 is an apocalyptic number.

21503423 is a deficient number, since it is larger than the sum of its proper divisors (1).

21503423 is an equidigital number, since it uses as much as digits as its factorization.

21503423 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 720, while the sum is 20.

The square root of 21503423 is about 4637.1783446402. The cubic root of 21503423 is about 278.0796443819.

Adding to 21503423 its reverse (32430512), we get a palindrome (53933935).

The spelling of 21503423 in words is "twenty-one million, five hundred three thousand, four hundred twenty-three".