21752121 has 4 divisors (see below), whose sum is σ = 29002832. Its totient is φ = 14501412.

The previous prime is 21752113. The next prime is 21752141. The reversal of 21752121 is 12125712.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 21752121 - 2³ = 21752113 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21752141) 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, 3625351 + ... + 3625356.

It is an arithmetic number, because the mean of its divisors is an integer number (7250708).

Almost surely, 2^21752121 is an apocalyptic number.

It is an amenable number.

21752121 is a deficient number, since it is larger than the sum of its proper divisors (7250711).

21752121 is an equidigital number, since it uses as much as digits as its factorization.

21752121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7250710.

The product of its digits is 280, while the sum is 21.

The square root of 21752121 is about 4663.9169160696. The cubic root of 21752121 is about 279.1475818938.

Adding to 21752121 its reverse (12125712), we get a palindrome (33877833).

The spelling of 21752121 in words is "twenty-one million, seven hundred fifty-two thousand, one hundred twenty-one".