21021111 has 6 divisors (see below), whose sum is σ = 30363840. Its totient is φ = 14014068.

The previous prime is 21021107. The next prime is 21021127. The reversal of 21021111 is 11112012.

It is a happy number.

It is not a de Polignac number, because 21021111 - 2² = 21021107 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (9), and also a Moran number because the ratio is a prime number: 2335679 = 21021111 / (2 + 1 + 0 + 2 + 1 + 1 + 1 + 1).

It is a junction number, because it is equal to n+sod(n) for n = 21021093 and 21021102.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21021101) 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 5 ways as a sum of consecutive naturals, for example, 1167831 + ... + 1167848.

It is an arithmetic number, because the mean of its divisors is an integer number (5060640).

Almost surely, 2^21021111 is an apocalyptic number.

21021111 is a deficient number, since it is larger than the sum of its proper divisors (9342729).

21021111 is a wasteful number, since it uses less digits than its factorization.

21021111 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2335685 (or 2335682 counting only the distinct ones).

The product of its (nonzero) digits is 4, while the sum is 9.

The square root of 21021111 is about 4584.8785152935. The cubic root of 21021111 is about 275.9848369111.

Adding to 21021111 its reverse (11112012), we get a palindrome (32133123).

Subtracting from 21021111 its reverse (11112012), we obtain a palindrome (9909099).

It can be divided in two parts, 210 and 21111, that added together give a triangular number (21321 = T₂₀₆).

The spelling of 21021111 in words is "twenty-one million, twenty-one thousand, one hundred eleven".