21316191 has 8 divisors (see below), whose sum is σ = 30607920. Its totient is φ = 13117632.

The previous prime is 21316177. The next prime is 21316199. The reversal of 21316191 is 19161312.

Added to its reverse (19161312) it gives a triangular number (40477503 = T₈₉₉₇).

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

It is not a de Polignac number, because 21316191 - 2⁷ = 21316063 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21316199) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 273246 + ... + 273323.

It is an arithmetic number, because the mean of its divisors is an integer number (3825990).

Almost surely, 2^21316191 is an apocalyptic number.

21316191 is a deficient number, since it is larger than the sum of its proper divisors (9291729).

21316191 is a wasteful number, since it uses less digits than its factorization.

21316191 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 546585.

The product of its digits is 324, while the sum is 24.

The square root of 21316191 is about 4616.9460685609. The cubic root of 21316191 is about 277.2702033958.

Adding to 21316191 its reverse (19161312), we get a triangular number (40477503 = T₈₉₉₇).

The spelling of 21316191 in words is "twenty-one million, three hundred sixteen thousand, one hundred ninety-one".