21121311 has 16 divisors (see below), whose sum is σ = 28811648. Its totient is φ = 13759200.

The previous prime is 21121277. The next prime is 21121319. The reversal of 21121311 is 11312112.

It is not a de Polignac number, because 21121311 - 2¹³ = 21113119 is a prime.

It is a super-2 number, since 2×21121311² = 892219556717442, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21121319) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 38340 + ... + 38886.

It is an arithmetic number, because the mean of its divisors is an integer number (1800728).

Almost surely, 2^21121311 is an apocalyptic number.

21121311 is a deficient number, since it is larger than the sum of its proper divisors (7690337).

21121311 is a wasteful number, since it uses less digits than its factorization.

21121311 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 822.

The product of its digits is 12, while the sum is 12.

The square root of 21121311 is about 4595.7927498964. The cubic root of 21121311 is about 276.4226485044.

Adding to 21121311 its reverse (11312112), we get a palindrome (32433423).

The spelling of 21121311 in words is "twenty-one million, one hundred twenty-one thousand, three hundred eleven".