21520747 has 2 divisors, whose sum is σ = 21520748. Its totient is φ = 21520746.

The previous prime is 21520729. The next prime is 21520771. The reversal of 21520747 is 74702512.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21520747 is a prime.

It is not a weakly prime, because it can be changed into another prime (21520547) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10760373 + 10760374.

It is an arithmetic number, because the mean of its divisors is an integer number (10760374).

Almost surely, 2^21520747 is an apocalyptic number.

21520747 is a deficient number, since it is larger than the sum of its proper divisors (1).

21520747 is an equidigital number, since it uses as much as digits as its factorization.

21520747 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 3920, while the sum is 28.

The square root of 21520747 is about 4639.0459148407. The cubic root of 21520747 is about 278.1543016218.

The spelling of 21520747 in words is "twenty-one million, five hundred twenty thousand, seven hundred forty-seven".