21321345 has 24 divisors (see below), whose sum is σ = 35675136. Its totient is φ = 10872928.

The previous prime is 21321341. The next prime is 21321359. The reversal of 21321345 is 54312312.

It is not a de Polignac number, because 21321345 - 2² = 21321341 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21321341) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 6592 + ... + 9278.

It is an arithmetic number, because the mean of its divisors is an integer number (1486464).

Almost surely, 2^21321345 is an apocalyptic number.

It is an amenable number.

21321345 is a deficient number, since it is larger than the sum of its proper divisors (14353791).

21321345 is a wasteful number, since it uses less digits than its factorization.

21321345 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2741 (or 2718 counting only the distinct ones).

The product of its digits is 720, while the sum is 21.

The square root of 21321345 is about 4617.5041959916. The cubic root of 21321345 is about 277.2925484678.

Adding to 21321345 its reverse (54312312), we get a palindrome (75633657).

The spelling of 21321345 in words is "twenty-one million, three hundred twenty-one thousand, three hundred forty-five".