21097123 has 4 divisors (see below), whose sum is σ = 21824640. Its totient is φ = 20369608.

The previous prime is 21097121. The next prime is 21097129. The reversal of 21097123 is 32179012.

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 21097123 - 2¹ = 21097121 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21097121) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 363715 + ... + 363772.

It is an arithmetic number, because the mean of its divisors is an integer number (5456160).

Almost surely, 2^21097123 is an apocalyptic number.

21097123 is a deficient number, since it is larger than the sum of its proper divisors (727517).

21097123 is an equidigital number, since it uses as much as digits as its factorization.

21097123 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 727516.

The product of its (nonzero) digits is 756, while the sum is 25.

The square root of 21097123 is about 4593.1604587691. The cubic root of 21097123 is about 276.3170890066.

The spelling of 21097123 in words is "twenty-one million, ninety-seven thousand, one hundred twenty-three".