21542623 has 2 divisors, whose sum is σ = 21542624. Its totient is φ = 21542622.

The previous prime is 21542597. The next prime is 21542639. The reversal of 21542623 is 32624512.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21542623 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21542663) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10771311 + 10771312.

It is an arithmetic number, because the mean of its divisors is an integer number (10771312).

Almost surely, 2^21542623 is an apocalyptic number.

21542623 is a deficient number, since it is larger than the sum of its proper divisors (1).

21542623 is an equidigital number, since it uses as much as digits as its factorization.

21542623 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2880, while the sum is 25.

The square root of 21542623 is about 4641.4031283654. The cubic root of 21542623 is about 278.2485183465.

The spelling of 21542623 in words is "twenty-one million, five hundred forty-two thousand, six hundred twenty-three".