21431091 has 8 divisors (see below), whose sum is σ = 31172544. Its totient is φ = 12988520.

The previous prime is 21431063. The next prime is 21431099. The reversal of 21431091 is 19013412.

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 21431091 - 2²² = 17236787 is a prime.

It is a super-2 number, since 2×21431091² = 918583322900562, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21431099) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 324681 + ... + 324746.

It is an arithmetic number, because the mean of its divisors is an integer number (3896568).

Almost surely, 2^21431091 is an apocalyptic number.

21431091 is a deficient number, since it is larger than the sum of its proper divisors (9741453).

21431091 is a wasteful number, since it uses less digits than its factorization.

21431091 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 649441.

The product of its (nonzero) digits is 216, while the sum is 21.

The square root of 21431091 is about 4629.3726356819. The cubic root of 21431091 is about 277.7674979248.

The spelling of 21431091 in words is "twenty-one million, four hundred thirty-one thousand, ninety-one".