21120397 has 4 divisors (see below), whose sum is σ = 21129696. Its totient is φ = 21111100.

The previous prime is 21120391. The next prime is 21120403. The reversal of 21120397 is 79302112.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also a brilliant number, because the two primes have the same length.

It is an interprime number because it is at equal distance from previous prime (21120391) and next prime (21120403).

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21120397 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 (21120391) 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, 1272 + ... + 6622.

It is an arithmetic number, because the mean of its divisors is an integer number (5282424).

Almost surely, 2^21120397 is an apocalyptic number.

It is an amenable number.

21120397 is a deficient number, since it is larger than the sum of its proper divisors (9299).

21120397 is an equidigital number, since it uses as much as digits as its factorization.

21120397 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9298.

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

The square root of 21120397 is about 4595.6933100458. The cubic root of 21120397 is about 276.4186611580.

The spelling of 21120397 in words is "twenty-one million, one hundred twenty thousand, three hundred ninety-seven".