21740591 has 4 divisors (see below), whose sum is σ = 21803592. Its totient is φ = 21677592.

The previous prime is 21740557. The next prime is 21740611. The reversal of 21740591 is 19504712.

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 21740591 - 2¹⁴ = 21724207 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21740491) 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, 30980 + ... + 31673.

It is an arithmetic number, because the mean of its divisors is an integer number (5450898).

Almost surely, 2^21740591 is an apocalyptic number.

21740591 is a deficient number, since it is larger than the sum of its proper divisors (63001).

21740591 is an equidigital number, since it uses as much as digits as its factorization.

21740591 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 63000.

The product of its (nonzero) digits is 2520, while the sum is 29.

The square root of 21740591 is about 4662.6806667410. The cubic root of 21740591 is about 279.0982512182.

The spelling of 21740591 in words is "twenty-one million, seven hundred forty thousand, five hundred ninety-one".