21545451 has 12 divisors (see below), whose sum is σ = 31845528. Its totient is φ = 14029344.

The previous prime is 21545441. The next prime is 21545471. The reversal of 21545451 is 15454512.

It is not a de Polignac number, because 21545451 - 2¹⁰ = 21544427 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21545441) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 27450 + ... + 28223.

It is an arithmetic number, because the mean of its divisors is an integer number (2653794).

Almost surely, 2^21545451 is an apocalyptic number.

21545451 is a deficient number, since it is larger than the sum of its proper divisors (10300077).

21545451 is a wasteful number, since it uses less digits than its factorization.

21545451 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 55722 (or 55719 counting only the distinct ones).

The product of its digits is 4000, while the sum is 27.

The square root of 21545451 is about 4641.7077676217. The cubic root of 21545451 is about 278.2606934714.

Adding to 21545451 its reverse (15454512), we get a palindrome (36999963).

The spelling of 21545451 in words is "twenty-one million, five hundred forty-five thousand, four hundred fifty-one".