21704993 has 4 divisors (see below), whose sum is σ = 21762048. Its totient is φ = 21647940.

The previous prime is 21704957. The next prime is 21704999. The reversal of 21704993 is 39940712.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21704993 - 2⁸ = 21704737 is a prime.

It is a super-2 number, since 2×21704993² = 942213442260098, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21704999) 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, 27953 + ... + 28718.

It is an arithmetic number, because the mean of its divisors is an integer number (5440512).

Almost surely, 2^21704993 is an apocalyptic number.

It is an amenable number.

21704993 is a deficient number, since it is larger than the sum of its proper divisors (57055).

21704993 is an equidigital number, since it uses as much as digits as its factorization.

21704993 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 57054.

The product of its (nonzero) digits is 13608, while the sum is 35.

The square root of 21704993 is about 4658.8617708621. The cubic root of 21704993 is about 278.9458363615.

The spelling of 21704993 in words is "twenty-one million, seven hundred four thousand, nine hundred ninety-three".