21545151 has 4 divisors (see below), whose sum is σ = 28726872. Its totient is φ = 14363432.

The previous prime is 21545149. The next prime is 21545179. The reversal of 21545151 is 15154512.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21545151 - 2¹ = 21545149 is a prime.

It is a super-2 number, since 2×21545151² = 928387063225602, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21545141) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3590856 + ... + 3590861.

It is an arithmetic number, because the mean of its divisors is an integer number (7181718).

Almost surely, 2^21545151 is an apocalyptic number.

21545151 is a deficient number, since it is larger than the sum of its proper divisors (7181721).

21545151 is an equidigital number, since it uses as much as digits as its factorization.

21545151 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7181720.

The product of its digits is 1000, while the sum is 24.

The square root of 21545151 is about 4641.6754518169. The cubic root of 21545151 is about 278.2594019599.

Adding to 21545151 its reverse (15154512), we get a palindrome (36699663).

The spelling of 21545151 in words is "twenty-one million, five hundred forty-five thousand, one hundred fifty-one".