21491421 has 32 divisors (see below), whose sum is σ = 34003200. Its totient is φ = 11819520.

The previous prime is 21491411. The next prime is 21491423. The reversal of 21491421 is 12419412.

It is not a de Polignac number, because 21491421 - 2¹¹ = 21489373 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21491391 and 21491400.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21491423) 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 31 ways as a sum of consecutive naturals, for example, 93735 + ... + 93963.

It is an arithmetic number, because the mean of its divisors is an integer number (1062600).

Almost surely, 2^21491421 is an apocalyptic number.

21491421 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

21491421 is a deficient number, since it is larger than the sum of its proper divisors (12511779).

21491421 is a wasteful number, since it uses less digits than its factorization.

21491421 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 389.

The product of its digits is 576, while the sum is 24.

The square root of 21491421 is about 4635.8840580843. The cubic root of 21491421 is about 278.0278986200.

It can be divided in two parts, 21491 and 421, that added together give a palindrome (21912).

The spelling of 21491421 in words is "twenty-one million, four hundred ninety-one thousand, four hundred twenty-one".