21097399 has 8 divisors (see below), whose sum is σ = 21526400. Its totient is φ = 20671200.

The previous prime is 21097393. The next prime is 21097421. The reversal of 21097399 is 99379012.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21097399 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21097393) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 20794 + ... + 21784.

It is an arithmetic number, because the mean of its divisors is an integer number (2690800).

Almost surely, 2^21097399 is an apocalyptic number.

21097399 is a deficient number, since it is larger than the sum of its proper divisors (429001).

21097399 is an equidigital number, since it uses as much as digits as its factorization.

21097399 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1401.

The product of its (nonzero) digits is 30618, while the sum is 40.

The square root of 21097399 is about 4593.1905033430. The cubic root of 21097399 is about 276.3182939605.

It can be divided in two parts, 2109 and 7399, that multiplied together give a triangular number (15604491 = T₅₅₈₆).

The spelling of 21097399 in words is "twenty-one million, ninety-seven thousand, three hundred ninety-nine".