21125191 has 6 divisors (see below), whose sum is σ = 21304976. Its totient is φ = 20946900.

The previous prime is 21125183. The next prime is 21125219. The reversal of 21125191 is 19152112.

It is not a de Polignac number, because 21125191 - 2³ = 21125183 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21125161) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 16546 + ... + 17776.

Almost surely, 2^21125191 is an apocalyptic number.

21125191 is a deficient number, since it is larger than the sum of its proper divisors (179785).

21125191 is an equidigital number, since it uses as much as digits as its factorization.

21125191 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1493 (or 1362 counting only the distinct ones).

The product of its digits is 180, while the sum is 22.

The square root of 21125191 is about 4596.2148557264. The cubic root of 21125191 is about 276.4395738144.

It can be divided in two parts, 21125 and 191, that added together give a square (21316 = 146²).

The spelling of 21125191 in words is "twenty-one million, one hundred twenty-five thousand, one hundred ninety-one".