21712393 has 2 divisors, whose sum is σ = 21712394. Its totient is φ = 21712392.

The previous prime is 21712381. The next prime is 21712423. The reversal of 21712393 is 39321712.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21641104 + 71289 = 4652^2 + 267^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21712393 is a prime.

It is not a weakly prime, because it can be changed into another prime (21712343) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10856196 + 10856197.

It is an arithmetic number, because the mean of its divisors is an integer number (10856197).

Almost surely, 2^21712393 is an apocalyptic number.

It is an amenable number.

21712393 is a deficient number, since it is larger than the sum of its proper divisors (1).

21712393 is an equidigital number, since it uses as much as digits as its factorization.

21712393 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2268, while the sum is 28.

The square root of 21712393 is about 4659.6558885823. The cubic root of 21712393 is about 278.9775335943.

The spelling of 21712393 in words is "twenty-one million, seven hundred twelve thousand, three hundred ninety-three".