21151211 has 4 divisors (see below), whose sum is σ = 21173712. Its totient is φ = 21128712.

The previous prime is 21151189. The next prime is 21151219. The reversal of 21151211 is 11215112.

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 21151211 - 2⁶ = 21151147 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21151219) 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, 9776 + ... + 11741.

It is an arithmetic number, because the mean of its divisors is an integer number (5293428).

Almost surely, 2^21151211 is an apocalyptic number.

21151211 is a deficient number, since it is larger than the sum of its proper divisors (22501).

21151211 is an equidigital number, since it uses as much as digits as its factorization.

21151211 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 22500.

The product of its digits is 20, while the sum is 14.

The square root of 21151211 is about 4599.0445746916. The cubic root of 21151211 is about 276.5530245682.

Adding to 21151211 its reverse (11215112), we get a palindrome (32366323).

The spelling of 21151211 in words is "twenty-one million, one hundred fifty-one thousand, two hundred eleven".