21138193 has 4 divisors (see below), whose sum is σ = 21163828. Its totient is φ = 21112560.

The previous prime is 21138179. The next prime is 21138209. The reversal of 21138193 is 39183112.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 3932289 + 17205904 = 1983^2 + 4148^2 .

It is a cyclic number.

It is not a de Polignac number, because 21138193 - 2¹³ = 21130001 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21138113) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 11538 + ... + 13243.

It is an arithmetic number, because the mean of its divisors is an integer number (5290957).

Almost surely, 2^21138193 is an apocalyptic number.

It is an amenable number.

21138193 is a deficient number, since it is larger than the sum of its proper divisors (25635).

21138193 is an equidigital number, since it uses as much as digits as its factorization.

21138193 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 25634.

The product of its digits is 1296, while the sum is 28.

The square root of 21138193 is about 4597.6290628975. The cubic root of 21138193 is about 276.4962759478.

The spelling of 21138193 in words is "twenty-one million, one hundred thirty-eight thousand, one hundred ninety-three".