21252139 has 2 divisors, whose sum is σ = 21252140. Its totient is φ = 21252138.

The previous prime is 21252137. The next prime is 21252149. The reversal of 21252139 is 93125212.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21252139 - 2¹ = 21252137 is a prime.

Together with 21252137, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (21252137) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10626069 + 10626070.

It is an arithmetic number, because the mean of its divisors is an integer number (10626070).

Almost surely, 2^21252139 is an apocalyptic number.

21252139 is a deficient number, since it is larger than the sum of its proper divisors (1).

21252139 is an equidigital number, since it uses as much as digits as its factorization.

21252139 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1080, while the sum is 25.

The square root of 21252139 is about 4610.0042299330. The cubic root of 21252139 is about 276.9922061173.

The spelling of 21252139 in words is "twenty-one million, two hundred fifty-two thousand, one hundred thirty-nine".