21383491 has 4 divisors (see below), whose sum is σ = 22313232. Its totient is φ = 20453752.

The previous prime is 21383473. The next prime is 21383497. The reversal of 21383491 is 19438312.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21383491 - 2⁷ = 21383363 is a prime.

It is a super-3 number, since 3×21383491³ (a number of 23 digits) contains 333 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21383497) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 464836 + ... + 464881.

It is an arithmetic number, because the mean of its divisors is an integer number (5578308).

Almost surely, 2^21383491 is an apocalyptic number.

21383491 is a deficient number, since it is larger than the sum of its proper divisors (929741).

21383491 is an equidigital number, since it uses as much as digits as its factorization.

21383491 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 929740.

The product of its digits is 5184, while the sum is 31.

The square root of 21383491 is about 4624.2286924416. The cubic root of 21383491 is about 277.5616982635.

The spelling of 21383491 in words is "twenty-one million, three hundred eighty-three thousand, four hundred ninety-one".