21711391 has 8 divisors (see below), whose sum is σ = 23442944. Its totient is φ = 19988640.

The previous prime is 21711331. The next prime is 21711419. The reversal of 21711391 is 19311712.

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 21711391 - 2¹⁵ = 21678623 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 (21711301) 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, 3490 + ... + 7456.

It is an arithmetic number, because the mean of its divisors is an integer number (2930368).

Almost surely, 2^21711391 is an apocalyptic number.

21711391 is a deficient number, since it is larger than the sum of its proper divisors (1731553).

21711391 is a wasteful number, since it uses less digits than its factorization.

21711391 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4401.

The product of its digits is 378, while the sum is 25.

The square root of 21711391 is about 4659.5483686727. The cubic root of 21711391 is about 278.9732420393.

The spelling of 21711391 in words is "twenty-one million, seven hundred eleven thousand, three hundred ninety-one".