21493387 has 2 divisors, whose sum is σ = 21493388. Its totient is φ = 21493386.

The previous prime is 21493363. The next prime is 21493441. The reversal of 21493387 is 78339412.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21493387 - 2⁷ = 21493259 is a prime.

It is not a weakly prime, because it can be changed into another prime (21493487) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10746693 + 10746694.

It is an arithmetic number, because the mean of its divisors is an integer number (10746694).

Almost surely, 2^21493387 is an apocalyptic number.

21493387 is a deficient number, since it is larger than the sum of its proper divisors (1).

21493387 is an equidigital number, since it uses as much as digits as its factorization.

21493387 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 36288, while the sum is 37.

The square root of 21493387 is about 4636.0960947763. The cubic root of 21493387 is about 278.0363762071.

The spelling of 21493387 in words is "twenty-one million, four hundred ninety-three thousand, three hundred eighty-seven".