21745547 has 2 divisors, whose sum is σ = 21745548. Its totient is φ = 21745546.

The previous prime is 21745543. The next prime is 21745561. The reversal of 21745547 is 74554712.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21745547 - 2² = 21745543 is a prime.

It is not a weakly prime, because it can be changed into another prime (21745543) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10872773 + 10872774.

It is an arithmetic number, because the mean of its divisors is an integer number (10872774).

Almost surely, 2^21745547 is an apocalyptic number.

21745547 is a deficient number, since it is larger than the sum of its proper divisors (1).

21745547 is an equidigital number, since it uses as much as digits as its factorization.

21745547 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 39200, while the sum is 35.

The square root of 21745547 is about 4663.2120903943. The cubic root of 21745547 is about 279.1194574164.

The spelling of 21745547 in words is "twenty-one million, seven hundred forty-five thousand, five hundred forty-seven".