21490421 has 8 divisors (see below), whose sum is σ = 22705920. Its totient is φ = 20306608.

The previous prime is 21490393. The next prime is 21490423. The reversal of 21490421 is 12409412.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21490421 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21490423) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 6521 + ... + 9246.

It is an arithmetic number, because the mean of its divisors is an integer number (2838240).

Almost surely, 2^21490421 is an apocalyptic number.

It is an amenable number.

21490421 is a deficient number, since it is larger than the sum of its proper divisors (1215499).

21490421 is a wasteful number, since it uses less digits than its factorization.

21490421 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 15843.

The product of its (nonzero) digits is 576, while the sum is 23.

The square root of 21490421 is about 4635.7762025361. The cubic root of 21490421 is about 278.0235863224.

Adding to 21490421 its reverse (12409412), we get a palindrome (33899833).

The spelling of 21490421 in words is "twenty-one million, four hundred ninety thousand, four hundred twenty-one".