21147823 has 2 divisors, whose sum is σ = 21147824. Its totient is φ = 21147822.

The previous prime is 21147811. The next prime is 21147827. The reversal of 21147823 is 32874112.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21147823 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21147791 and 21147800.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21147827) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10573911 + 10573912.

It is an arithmetic number, because the mean of its divisors is an integer number (10573912).

Almost surely, 2^21147823 is an apocalyptic number.

21147823 is a deficient number, since it is larger than the sum of its proper divisors (1).

21147823 is an equidigital number, since it uses as much as digits as its factorization.

21147823 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2688, while the sum is 28.

The square root of 21147823 is about 4598.6762225667. The cubic root of 21147823 is about 276.5382576961.

The spelling of 21147823 in words is "twenty-one million, one hundred forty-seven thousand, eight hundred twenty-three".