21345451 has 2 divisors, whose sum is σ = 21345452. Its totient is φ = 21345450.

The previous prime is 21345431. The next prime is 21345469. The reversal of 21345451 is 15454312.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21345451 is a prime.

It is not a weakly prime, because it can be changed into another prime (21345431) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10672725 + 10672726.

It is an arithmetic number, because the mean of its divisors is an integer number (10672726).

Almost surely, 2^21345451 is an apocalyptic number.

21345451 is a deficient number, since it is larger than the sum of its proper divisors (1).

21345451 is an equidigital number, since it uses as much as digits as its factorization.

21345451 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2400, while the sum is 25.

The square root of 21345451 is about 4620.1137431886. The cubic root of 21345451 is about 277.3970118059.

Adding to 21345451 its reverse (15454312), we get a palindrome (36799763).

The spelling of 21345451 in words is "twenty-one million, three hundred forty-five thousand, four hundred fifty-one".