21532251 has 32 divisors (see below), whose sum is σ = 33481728. Its totient is φ = 12188160.

The previous prime is 21532249. The next prime is 21532271. The reversal of 21532251 is 15223512.

It is not a de Polignac number, because 21532251 - 2¹ = 21532249 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21532201) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 30816 + ... + 31506.

It is an arithmetic number, because the mean of its divisors is an integer number (1046304).

Almost surely, 2^21532251 is an apocalyptic number.

21532251 is a deficient number, since it is larger than the sum of its proper divisors (11949477).

21532251 is a wasteful number, since it uses less digits than its factorization.

21532251 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 771.

The product of its digits is 600, while the sum is 21.

The square root of 21532251 is about 4640.2856593102. The cubic root of 21532251 is about 278.2038556187.

Adding to 21532251 its reverse (15223512), we get a palindrome (36755763).

The spelling of 21532251 in words is "twenty-one million, five hundred thirty-two thousand, two hundred fifty-one".