21340891 has 12 divisors (see below), whose sum is σ = 25263616. Its totient is φ = 17907120.

The previous prime is 21340889. The next prime is 21340931. The reversal of 21340891 is 19804312.

It is a happy number.

It is not a de Polignac number, because 21340891 - 2¹ = 21340889 is a prime.

It is a hoax number, since the sum of its digits (28) coincides with the sum of the digits of its distinct prime factors.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21340801) 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 11 ways as a sum of consecutive naturals, for example, 5211 + ... + 8356.

Almost surely, 2^21340891 is an apocalyptic number.

21340891 is a deficient number, since it is larger than the sum of its proper divisors (3922725).

21340891 is a wasteful number, since it uses less digits than its factorization.

21340891 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 13602 (or 13591 counting only the distinct ones).

The product of its (nonzero) digits is 1728, while the sum is 28.

The square root of 21340891 is about 4619.6202224858. The cubic root of 21340891 is about 277.3772570822.

The spelling of 21340891 in words is "twenty-one million, three hundred forty thousand, eight hundred ninety-one".