21138473 has 2 divisors, whose sum is σ = 21138474. Its totient is φ = 21138472.

The previous prime is 21138451. The next prime is 21138503. The reversal of 21138473 is 37483112.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 18983449 + 2155024 = 4357^2 + 1468^2 .

It is a cyclic number.

It is not a de Polignac number, because 21138473 - 2⁶ = 21138409 is a prime.

It is not a weakly prime, because it can be changed into another prime (21138443) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10569236 + 10569237.

It is an arithmetic number, because the mean of its divisors is an integer number (10569237).

Almost surely, 2^21138473 is an apocalyptic number.

It is an amenable number.

21138473 is a deficient number, since it is larger than the sum of its proper divisors (1).

21138473 is an equidigital number, since it uses as much as digits as its factorization.

21138473 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 4032, while the sum is 29.

The square root of 21138473 is about 4597.6595132741. The cubic root of 21138473 is about 276.4974967809.

The spelling of 21138473 in words is "twenty-one million, one hundred thirty-eight thousand, four hundred seventy-three".