21921123 has 32 divisors (see below), whose sum is σ = 34865152. Its totient is φ = 11988000.

The previous prime is 21921121. The next prime is 21921167. The reversal of 21921123 is 32112912.

It is a Cunningham number, because it is equal to 4682²-1.

It is not a de Polignac number, because 21921123 - 2¹ = 21921121 is a prime.

It is a super-2 number, since 2×21921123² = 961071267162258, which contains 22 as substring.

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

It is a self number, because there is not a number n which added to its sum of digits gives 21921123.

It is not an unprimeable number, because it can be changed into a prime (21921121) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 98190 + ... + 98412.

It is an arithmetic number, because the mean of its divisors is an integer number (1089536).

Almost surely, 2^21921123 is an apocalyptic number.

21921123 is a deficient number, since it is larger than the sum of its proper divisors (12944029).

21921123 is a wasteful number, since it uses less digits than its factorization.

21921123 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 415.

The product of its digits is 216, while the sum is 21.

The square root of 21921123 is about 4681.9998932080. Note that the first 3 decimals coincide. The cubic root of 21921123 is about 279.8686586386.

The spelling of 21921123 in words is "twenty-one million, nine hundred twenty-one thousand, one hundred twenty-three".