21740647 has 2 divisors, whose sum is σ = 21740648. Its totient is φ = 21740646.

The previous prime is 21740639. The next prime is 21740659. The reversal of 21740647 is 74604712.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21740647 - 2³ = 21740639 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21740627) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10870323 + 10870324.

It is an arithmetic number, because the mean of its divisors is an integer number (10870324).

Almost surely, 2^21740647 is an apocalyptic number.

21740647 is a deficient number, since it is larger than the sum of its proper divisors (1).

21740647 is an equidigital number, since it uses as much as digits as its factorization.

21740647 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 9408, while the sum is 31.

The square root of 21740647 is about 4662.6866718663. The cubic root of 21740647 is about 279.0984908543.

The spelling of 21740647 in words is "twenty-one million, seven hundred forty thousand, six hundred forty-seven".