21491131 has 8 divisors (see below), whose sum is σ = 22626720. Its totient is φ = 20372352.

The previous prime is 21491101. The next prime is 21491149. The reversal of 21491131 is 13119412.

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 21491131 - 2¹⁵ = 21458363 is a prime.

It is a super-2 number, since 2×21491131² = 923737423318322, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21491101) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1536 + ... + 6733.

It is an arithmetic number, because the mean of its divisors is an integer number (2828340).

Almost surely, 2^21491131 is an apocalyptic number.

21491131 is a deficient number, since it is larger than the sum of its proper divisors (1135589).

21491131 is a wasteful number, since it uses less digits than its factorization.

21491131 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8405.

The product of its digits is 216, while the sum is 22.

The square root of 21491131 is about 4635.8527802336. The cubic root of 21491131 is about 278.0266480675.

The spelling of 21491131 in words is "twenty-one million, four hundred ninety-one thousand, one hundred thirty-one".