21020397 has 4 divisors (see below), whose sum is σ = 28027200. Its totient is φ = 14013596.

The previous prime is 21020369. The next prime is 21020407. The reversal of 21020397 is 79302012.

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.

It is a cyclic number.

It is not a de Polignac number, because 21020397 - 2⁷ = 21020269 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21025397) 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, 3503397 + ... + 3503402.

It is an arithmetic number, because the mean of its divisors is an integer number (7006800).

Almost surely, 2^21020397 is an apocalyptic number.

It is an amenable number.

21020397 is a deficient number, since it is larger than the sum of its proper divisors (7006803).

21020397 is an equidigital number, since it uses as much as digits as its factorization.

21020397 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7006802.

The product of its (nonzero) digits is 756, while the sum is 24.

The square root of 21020397 is about 4584.8006499738. The cubic root of 21020397 is about 275.9817121888.

The spelling of 21020397 in words is "twenty-one million, twenty thousand, three hundred ninety-seven".