21250139 has 2 divisors, whose sum is σ = 21250140. Its totient is φ = 21250138.

The previous prime is 21250133. The next prime is 21250171. The reversal of 21250139 is 93105212.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21250139 - 2⁴ = 21250123 is a prime.

It is not a weakly prime, because it can be changed into another prime (21250133) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10625069 + 10625070.

It is an arithmetic number, because the mean of its divisors is an integer number (10625070).

Almost surely, 2^21250139 is an apocalyptic number.

21250139 is a deficient number, since it is larger than the sum of its proper divisors (1).

21250139 is an equidigital number, since it uses as much as digits as its factorization.

21250139 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 540, while the sum is 23.

The square root of 21250139 is about 4609.7873052886. The cubic root of 21250139 is about 276.9835167678.

The spelling of 21250139 in words is "twenty-one million, two hundred fifty thousand, one hundred thirty-nine".