21139705 has 8 divisors (see below), whose sum is σ = 25715592. Its totient is φ = 16679808.

The previous prime is 21139667. The next prime is 21139709. The reversal of 21139705 is 50793112.

It can be written as a sum of positive squares in 4 ways, for example, as 3767481 + 17372224 = 1941^2 + 4168^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21139705 - 2⁷ = 21139577 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21139709) 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 7 ways as a sum of consecutive naturals, for example, 28594 + ... + 29323.

It is an arithmetic number, because the mean of its divisors is an integer number (3214449).

Almost surely, 2^21139705 is an apocalyptic number.

It is an amenable number.

21139705 is a deficient number, since it is larger than the sum of its proper divisors (4575887).

21139705 is an equidigital number, since it uses as much as digits as its factorization.

21139705 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 57995.

The product of its (nonzero) digits is 1890, while the sum is 28.

The square root of 21139705 is about 4597.7934925353. The cubic root of 21139705 is about 276.5028683184.

The spelling of 21139705 in words is "twenty-one million, one hundred thirty-nine thousand, seven hundred five".