21398423 has 2 divisors, whose sum is σ = 21398424. Its totient is φ = 21398422.

The previous prime is 21398413. The next prime is 21398437. The reversal of 21398423 is 32489312.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21398423 - 2¹² = 21394327 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21398423.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21398413) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10699211 + 10699212.

It is an arithmetic number, because the mean of its divisors is an integer number (10699212).

Almost surely, 2^21398423 is an apocalyptic number.

21398423 is a deficient number, since it is larger than the sum of its proper divisors (1).

21398423 is an equidigital number, since it uses as much as digits as its factorization.

21398423 is an evil number, because the sum of its binary digits is even.

The product of its digits is 10368, while the sum is 32.

The square root of 21398423 is about 4625.8429502092. The cubic root of 21398423 is about 277.6262899454.

The spelling of 21398423 in words is "twenty-one million, three hundred ninety-eight thousand, four hundred twenty-three".