21121993 has 8 divisors (see below), whose sum is σ = 21530880. Its totient is φ = 20716800.

The previous prime is 21121979. The next prime is 21121999. The reversal of 21121993 is 39912112.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21121993 is a prime.

It is a super-2 number, since 2×21121993² = 892277176584098, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21121999) 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 7 ways as a sum of consecutive naturals, for example, 12393 + ... + 13993.

It is an arithmetic number, because the mean of its divisors is an integer number (2691360).

Almost surely, 2^21121993 is an apocalyptic number.

It is an amenable number.

21121993 is a deficient number, since it is larger than the sum of its proper divisors (408887).

21121993 is a wasteful number, since it uses less digits than its factorization.

21121993 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1847.

The product of its digits is 972, while the sum is 28.

The square root of 21121993 is about 4595.8669475954. The cubic root of 21121993 is about 276.4256236703.

The spelling of 21121993 in words is "twenty-one million, one hundred twenty-one thousand, nine hundred ninety-three".