21312673 has 2 divisors, whose sum is σ = 21312674. Its totient is φ = 21312672.

The previous prime is 21312671. The next prime is 21312677. The reversal of 21312673 is 37621312.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20358144 + 954529 = 4512^2 + 977^2 .

It is a cyclic number.

It is not a de Polignac number, because 21312673 - 2¹ = 21312671 is a prime.

Together with 21312671, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (21312671) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10656336 + 10656337.

It is an arithmetic number, because the mean of its divisors is an integer number (10656337).

Almost surely, 2^21312673 is an apocalyptic number.

It is an amenable number.

21312673 is a deficient number, since it is larger than the sum of its proper divisors (1).

21312673 is an equidigital number, since it uses as much as digits as its factorization.

21312673 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1512, while the sum is 25.

The square root of 21312673 is about 4616.5650650673. The cubic root of 21312673 is about 277.2549491032.

Adding to 21312673 its reverse (37621312), we get a palindrome (58933985).

The spelling of 21312673 in words is "twenty-one million, three hundred twelve thousand, six hundred seventy-three".