21351421 has 32 divisors (see below), whose sum is σ = 28304640. Its totient is φ = 15634944.

The previous prime is 21351413. The next prime is 21351433. The reversal of 21351421 is 12415312.

It is not a de Polignac number, because 21351421 - 2³ = 21351413 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (19).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21351401) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 91521 + ... + 91753.

It is an arithmetic number, because the mean of its divisors is an integer number (884520).

Almost surely, 2^21351421 is an apocalyptic number.

It is an amenable number.

21351421 is a deficient number, since it is larger than the sum of its proper divisors (6953219).

21351421 is a wasteful number, since it uses less digits than its factorization.

21351421 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 325.

The product of its digits is 240, while the sum is 19.

The square root of 21351421 is about 4620.7597860092. The cubic root of 21351421 is about 277.4228706456.

Adding to 21351421 its reverse (12415312), we get a palindrome (33766733).

The spelling of 21351421 in words is "twenty-one million, three hundred fifty-one thousand, four hundred twenty-one".