21015139 has 2 divisors, whose sum is σ = 21015140. Its totient is φ = 21015138.

The previous prime is 21015119. The next prime is 21015143. The reversal of 21015139 is 93151012.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21015139 - 2⁷ = 21015011 is a prime.

It is not a weakly prime, because it can be changed into another prime (21015119) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10507569 + 10507570.

It is an arithmetic number, because the mean of its divisors is an integer number (10507570).

Almost surely, 2^21015139 is an apocalyptic number.

21015139 is a deficient number, since it is larger than the sum of its proper divisors (1).

21015139 is an equidigital number, since it uses as much as digits as its factorization.

21015139 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 270, while the sum is 22.

The square root of 21015139 is about 4584.2271976856. The cubic root of 21015139 is about 275.9586990990.

The spelling of 21015139 in words is "twenty-one million, fifteen thousand, one hundred thirty-nine".