21153993 has 16 divisors (see below), whose sum is σ = 32471040. Its totient is φ = 11999376.

The previous prime is 21153971. The next prime is 21154019. The reversal of 21153993 is 39935112.

It is not a de Polignac number, because 21153993 - 2⁶ = 21153929 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21153493) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 705 + ... + 6542.

It is an arithmetic number, because the mean of its divisors is an integer number (2029440).

Almost surely, 2^21153993 is an apocalyptic number.

It is an amenable number.

21153993 is a deficient number, since it is larger than the sum of its proper divisors (11317047).

21153993 is a wasteful number, since it uses less digits than its factorization.

21153993 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7396.

The product of its digits is 7290, while the sum is 33.

The square root of 21153993 is about 4599.3470188713. The cubic root of 21153993 is about 276.5651489612.

The spelling of 21153993 in words is "twenty-one million, one hundred fifty-three thousand, nine hundred ninety-three".