21272145 has 16 divisors (see below), whose sum is σ = 34167552. Its totient is φ = 11301120.

The previous prime is 21272129. The next prime is 21272149. The reversal of 21272145 is 54127212.

It is not a de Polignac number, because 21272145 - 2⁴ = 21272129 is a prime.

It is an alternating number because its digits alternate between even and odd.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21272149) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1449 + ... + 6681.

It is an arithmetic number, because the mean of its divisors is an integer number (2135472).

Almost surely, 2^21272145 is an apocalyptic number.

It is an amenable number.

21272145 is a deficient number, since it is larger than the sum of its proper divisors (12895407).

21272145 is a wasteful number, since it uses less digits than its factorization.

21272145 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5512.

The product of its digits is 1120, while the sum is 24.

The square root of 21272145 is about 4612.1735656846. The cubic root of 21272145 is about 277.0790956946.

Adding to 21272145 its reverse (54127212), we get a palindrome (75399357).

The spelling of 21272145 in words is "twenty-one million, two hundred seventy-two thousand, one hundred forty-five".