21321405 has 48 divisors (see below), whose sum is σ = 42681600. Its totient is φ = 9644544.

The previous prime is 21321379. The next prime is 21321407. The reversal of 21321405 is 50412312.

It is not a de Polignac number, because 21321405 - 2⁶ = 21321341 is a prime.

It is a super-2 number, since 2×21321405² = 909204622348050, which contains 22 as substring.

It is a plaindrome in base 16.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21321407) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 35296 + ... + 35894.

It is an arithmetic number, because the mean of its divisors is an integer number (889200).

Almost surely, 2^21321405 is an apocalyptic number.

It is an amenable number.

21321405 is a primitive abundant number, since it is smaller than the sum of its proper divisors, none of which is abundant.

21321405 is a wasteful number, since it uses less digits than its factorization.

21321405 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 730 (or 727 counting only the distinct ones).

The product of its (nonzero) digits is 240, while the sum is 18.

The square root of 21321405 is about 4617.5106930033. The cubic root of 21321405 is about 277.2928085755.

Adding to 21321405 its reverse (50412312), we get a palindrome (71733717).

The spelling of 21321405 in words is "twenty-one million, three hundred twenty-one thousand, four hundred five".