21611491 has 8 divisors (see below), whose sum is σ = 23698224. Its totient is φ = 19545120.

The previous prime is 21611461. The next prime is 21611519. The reversal of 21611491 is 19411612.

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 21611491 - 2¹³ = 21603299 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21611411) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2820 + ... + 7153.

It is an arithmetic number, because the mean of its divisors is an integer number (2962278).

Almost surely, 2^21611491 is an apocalyptic number.

21611491 is a deficient number, since it is larger than the sum of its proper divisors (2086733).

21611491 is a wasteful number, since it uses less digits than its factorization.

21611491 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10181.

The product of its digits is 432, while the sum is 25.

The square root of 21611491 is about 4648.8160858438. The cubic root of 21611491 is about 278.5447069074.

The spelling of 21611491 in words is "twenty-one million, six hundred eleven thousand, four hundred ninety-one".