21000393 has 6 divisors (see below), whose sum is σ = 30333914. Its totient is φ = 14000256.

The previous prime is 21000391. The next prime is 21000407. The reversal of 21000393 is 39300012.

It can be written as a sum of positive squares in only one way, i.e., 15468489 + 5531904 = 3933^2 + 2352^2 .

It is not a de Polignac number, because 21000393 - 2¹ = 21000391 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21000391) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1166680 + ... + 1166697.

Almost surely, 2^21000393 is an apocalyptic number.

It is an amenable number.

21000393 is a deficient number, since it is larger than the sum of its proper divisors (9333521).

21000393 is a wasteful number, since it uses less digits than its factorization.

21000393 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2333383 (or 2333380 counting only the distinct ones).

The product of its (nonzero) digits is 162, while the sum is 18.

The square root of 21000393 is about 4582.6185745707. The cubic root of 21000393 is about 275.8941386706.

The spelling of 21000393 in words is "twenty-one million, three hundred ninety-three", and thus it is an aban number.