21097723 has 2 divisors, whose sum is σ = 21097724. Its totient is φ = 21097722.

The previous prime is 21097667. The next prime is 21097753. The reversal of 21097723 is 32779012.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21097723 - 2¹³ = 21089531 is a prime.

It is a super-2 number, since 2×21097723² = 890227831569458, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21097753) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10548861 + 10548862.

It is an arithmetic number, because the mean of its divisors is an integer number (10548862).

Almost surely, 2^21097723 is an apocalyptic number.

21097723 is a deficient number, since it is larger than the sum of its proper divisors (1).

21097723 is an equidigital number, since it uses as much as digits as its factorization.

21097723 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 5292, while the sum is 31.

The square root of 21097723 is about 4593.2257728093. The cubic root of 21097723 is about 276.3197084582.

The spelling of 21097723 in words is "twenty-one million, ninety-seven thousand, seven hundred twenty-three".