21706791 has 4 divisors (see below), whose sum is σ = 28942392. Its totient is φ = 14471192.

The previous prime is 21706777. The next prime is 21706813. The reversal of 21706791 is 19760712.

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

It is a cyclic number.

It is not a de Polignac number, because 21706791 - 2¹⁴ = 21690407 is a prime.

It is a super-3 number, since 3×21706791³ (a number of 23 digits) contains 333 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21706591) 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, 3617796 + ... + 3617801.

It is an arithmetic number, because the mean of its divisors is an integer number (7235598).

Almost surely, 2^21706791 is an apocalyptic number.

21706791 is a deficient number, since it is larger than the sum of its proper divisors (7235601).

21706791 is an equidigital number, since it uses as much as digits as its factorization.

21706791 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7235600.

The product of its (nonzero) digits is 5292, while the sum is 33.

The square root of 21706791 is about 4659.0547324538. The cubic root of 21706791 is about 278.9535385949.

The spelling of 21706791 in words is "twenty-one million, seven hundred six thousand, seven hundred ninety-one".