21029993 has 4 divisors (see below), whose sum is σ = 21164100. Its totient is φ = 20895888.

The previous prime is 21029977. The next prime is 21030001. The reversal of 21029993 is 39992012.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 10291264 + 10738729 = 3208^2 + 3277^2 .

It is a cyclic number.

It is not a de Polignac number, because 21029993 - 2⁴ = 21029977 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21019993) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 66818 + ... + 67131.

It is an arithmetic number, because the mean of its divisors is an integer number (5291025).

Almost surely, 2^21029993 is an apocalyptic number.

It is an amenable number.

21029993 is a deficient number, since it is larger than the sum of its proper divisors (134107).

21029993 is a wasteful number, since it uses less digits than its factorization.

21029993 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 134106.

The product of its (nonzero) digits is 8748, while the sum is 35.

The square root of 21029993 is about 4585.8470319015. The cubic root of 21029993 is about 276.0237018433.

It can be divided in two parts, 21029 and 993, that added together give a palindrome (22022).

The spelling of 21029993 in words is "twenty-one million, twenty-nine thousand, nine hundred ninety-three".