21121275 has 24 divisors (see below), whose sum is σ = 39910144. Its totient is φ = 9655200.

The previous prime is 21121271. The next prime is 21121277. The reversal of 21121275 is 57212112.

It is not a de Polignac number, because 21121275 - 2² = 21121271 is a prime.

It is a super-2 number, since 2×21121275² = 892216515251250, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (21).

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21121271) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 19591 + ... + 20640.

Almost surely, 2^21121275 is an apocalyptic number.

21121275 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

21121275 is a deficient number, since it is larger than the sum of its proper divisors (18788869).

21121275 is a wasteful number, since it uses less digits than its factorization.

21121275 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 40251 (or 40246 counting only the distinct ones).

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

The square root of 21121275 is about 4595.7888332690. The cubic root of 21121275 is about 276.4224914557.

Adding to 21121275 its reverse (57212112), we get a palindrome (78333387).

The spelling of 21121275 in words is "twenty-one million, one hundred twenty-one thousand, two hundred seventy-five".