21438673 has 2 divisors, whose sum is σ = 21438674. Its totient is φ = 21438672.

The previous prime is 21438647. The next prime is 21438689. The reversal of 21438673 is 37683412.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 18558864 + 2879809 = 4308^2 + 1697^2 .

It is a cyclic number.

It is not a de Polignac number, because 21438673 - 2¹³ = 21430481 is a prime.

It is not a weakly prime, because it can be changed into another prime (21438623) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10719336 + 10719337.

It is an arithmetic number, because the mean of its divisors is an integer number (10719337).

Almost surely, 2^21438673 is an apocalyptic number.

It is an amenable number.

21438673 is a deficient number, since it is larger than the sum of its proper divisors (1).

21438673 is an equidigital number, since it uses as much as digits as its factorization.

21438673 is an evil number, because the sum of its binary digits is even.

The product of its digits is 24192, while the sum is 34.

The square root of 21438673 is about 4630.1914647237. The cubic root of 21438673 is about 277.8002507270.

It can be divided in two parts, 2143 and 8673, that added together give a square (10816 = 104²).

The spelling of 21438673 in words is "twenty-one million, four hundred thirty-eight thousand, six hundred seventy-three".