21138711 has 16 divisors (see below), whose sum is σ = 30915840. Its totient is φ = 12741120.

The previous prime is 21138619. The next prime is 21138713. The reversal of 21138711 is 11783112.

It is a happy number.

It is not a de Polignac number, because 21138711 - 2¹⁰ = 21137687 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21138713) 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 in 15 ways as a sum of consecutive naturals, for example, 4710 + ... + 8028.

It is an arithmetic number, because the mean of its divisors is an integer number (1932240).

Almost surely, 2^21138711 is an apocalyptic number.

21138711 is a deficient number, since it is larger than the sum of its proper divisors (9777129).

21138711 is a wasteful number, since it uses less digits than its factorization.

21138711 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3526.

The product of its digits is 336, while the sum is 24.

The square root of 21138711 is about 4597.6853959357. The cubic root of 21138711 is about 276.4985344805.

The spelling of 21138711 in words is "twenty-one million, one hundred thirty-eight thousand, seven hundred eleven".