21070397 has 4 divisors (see below), whose sum is σ = 21127260. Its totient is φ = 21013536.

The previous prime is 21070393. The next prime is 21070403. The reversal of 21070397 is 79307012.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 8637721 + 12432676 = 2939^2 + 3526^2 .

It is a cyclic number.

It is not a de Polignac number, because 21070397 - 2² = 21070393 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 (21070393) 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, 27872 + ... + 28617.

It is an arithmetic number, because the mean of its divisors is an integer number (5281815).

Almost surely, 2^21070397 is an apocalyptic number.

It is an amenable number.

21070397 is a deficient number, since it is larger than the sum of its proper divisors (56863).

21070397 is an equidigital number, since it uses as much as digits as its factorization.

21070397 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 56862.

The product of its (nonzero) digits is 2646, while the sum is 29.

The square root of 21070397 is about 4590.2502110451. The cubic root of 21070397 is about 276.2003594867.

It can be divided in two parts, 210 and 70397, that added together give a palindrome (70607).

The spelling of 21070397 in words is "twenty-one million, seventy thousand, three hundred ninety-seven".