21139975 has 6 divisors (see below), whose sum is σ = 26213600. Its totient is φ = 16911960.

The previous prime is 21139957. The next prime is 21139981. The reversal of 21139975 is 57993112.

It is not a de Polignac number, because 21139975 - 2¹¹ = 21137927 is a prime.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 422775 + ... + 422824.

Almost surely, 2^21139975 is an apocalyptic number.

21139975 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

21139975 is a deficient number, since it is larger than the sum of its proper divisors (5073625).

21139975 is an equidigital number, since it uses as much as digits as its factorization.

21139975 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 845609 (or 845604 counting only the distinct ones).

The product of its digits is 17010, while the sum is 37.

The square root of 21139975 is about 4597.8228543518. The cubic root of 21139975 is about 276.5040454943.

It can be divided in two parts, 211 and 39975, that added together give a triangular number (40186 = T₂₈₃).

The spelling of 21139975 in words is "twenty-one million, one hundred thirty-nine thousand, nine hundred seventy-five".