21740447 has 4 divisors (see below), whose sum is σ = 21756000. Its totient is φ = 21724896.

The previous prime is 21740443. The next prime is 21740449. The reversal of 21740447 is 74404712.

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 21740447 - 2² = 21740443 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 (21740443) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 5447 + ... + 8552.

It is an arithmetic number, because the mean of its divisors is an integer number (5439000).

Almost surely, 2^21740447 is an apocalyptic number.

21740447 is a deficient number, since it is larger than the sum of its proper divisors (15553).

21740447 is a wasteful number, since it uses less digits than its factorization.

21740447 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 15552.

The product of its (nonzero) digits is 6272, while the sum is 29.

The square root of 21740447 is about 4662.6652249545. The cubic root of 21740447 is about 279.0976350093.

The spelling of 21740447 in words is "twenty-one million, seven hundred forty thousand, four hundred forty-seven".