21051111 has 8 divisors (see below), whose sum is σ = 28101744. Its totient is φ = 14017280.

The previous prime is 21051103. The next prime is 21051137. The reversal of 21051111 is 11115012.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21051111 - 2³ = 21051103 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21051101) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 906 + ... + 6551.

It is an arithmetic number, because the mean of its divisors is an integer number (3512718).

Almost surely, 2^21051111 is an apocalyptic number.

21051111 is a deficient number, since it is larger than the sum of its proper divisors (7050633).

21051111 is an equidigital number, since it uses as much as digits as its factorization.

21051111 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8401.

The product of its (nonzero) digits is 10, while the sum is 12.

The square root of 21051111 is about 4588.1489731699. The cubic root of 21051111 is about 276.1160638722.

Adding to 21051111 its reverse (11115012), we get a palindrome (32166123).

The spelling of 21051111 in words is "twenty-one million, fifty-one thousand, one hundred eleven".