21111993 has 30 divisors (see below), whose sum is σ = 35611914. Its totient is φ = 12051648.

The previous prime is 21111991. The next prime is 21112009. The reversal of 21111993 is 39911112.

It can be written as a sum of positive squares in only one way, i.e., 20766249 + 345744 = 4557^2 + 588^2 .

It is not a de Polignac number, because 21111993 - 2¹ = 21111991 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21111991) by changing a digit.

It is a polite number, since it can be written in 29 ways as a sum of consecutive naturals, for example, 21121 + ... + 22097.

Almost surely, 2^21111993 is an apocalyptic number.

It is an amenable number.

21111993 is a deficient number, since it is larger than the sum of its proper divisors (14499921).

21111993 is an frugal number, since it uses more digits than its factorization.

21111993 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1011 (or 987 counting only the distinct ones).

The product of its digits is 486, while the sum is 27.

The square root of 21111993 is about 4594.7788847778. The cubic root of 21111993 is about 276.3819931192.

The spelling of 21111993 in words is "twenty-one million, one hundred eleven thousand, nine hundred ninety-three".