21750397 has 2 divisors, whose sum is σ = 21750398. Its totient is φ = 21750396.

The previous prime is 21750373. The next prime is 21750403. The reversal of 21750397 is 79305712.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 11978521 + 9771876 = 3461^2 + 3126^2 .

It is a cyclic number.

It is not a de Polignac number, because 21750397 - 2¹⁵ = 21717629 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21750347) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10875198 + 10875199.

It is an arithmetic number, because the mean of its divisors is an integer number (10875199).

Almost surely, 2^21750397 is an apocalyptic number.

It is an amenable number.

21750397 is a deficient number, since it is larger than the sum of its proper divisors (1).

21750397 is an equidigital number, since it uses as much as digits as its factorization.

21750397 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 13230, while the sum is 34.

The square root of 21750397 is about 4663.7320892178. The cubic root of 21750397 is about 279.1402069326.

The spelling of 21750397 in words is "twenty-one million, seven hundred fifty thousand, three hundred ninety-seven".