21974399 has 4 divisors (see below), whose sum is σ = 22029600. Its totient is φ = 21919200.

The previous prime is 21974369. The next prime is 21974413. The reversal of 21974399 is 99347912.

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 21974399 - 2¹² = 21970303 is a prime.

It is a super-2 number, since 2×21974399² = 965748422822402, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21974369) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 26999 + ... + 27800.

It is an arithmetic number, because the mean of its divisors is an integer number (5507400).

Almost surely, 2^21974399 is an apocalyptic number.

21974399 is a deficient number, since it is larger than the sum of its proper divisors (55201).

21974399 is an equidigital number, since it uses as much as digits as its factorization.

21974399 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 55200.

The product of its digits is 122472, while the sum is 44.

The square root of 21974399 is about 4687.6858896475. The cubic root of 21974399 is about 280.0952014709.

The spelling of 21974399 in words is "twenty-one million, nine hundred seventy-four thousand, three hundred ninety-nine".