21970321 has 4 divisors (see below), whose sum is σ = 21980644. Its totient is φ = 21960000.

The previous prime is 21970303. The next prime is 21970339. The reversal of 21970321 is 12307912.

It is a semiprime because it is the product of two primes, 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 (21970303) and next prime (21970339).

It can be written as a sum of positive squares in 2 ways, for example, as 3651921 + 18318400 = 1911^2 + 4280^2 .

It is a cyclic number.

It is not a de Polignac number, because 21970321 - 2¹⁷ = 21839249 is a prime.

It is a Duffinian number.

It is a plaindrome in base 11.

It is not an unprimeable number, because it can be changed into a prime (21970391) 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, 660 + ... + 6661.

It is an arithmetic number, because the mean of its divisors is an integer number (5495161).

Almost surely, 2^21970321 is an apocalyptic number.

It is an amenable number.

21970321 is a deficient number, since it is larger than the sum of its proper divisors (10323).

21970321 is an equidigital number, since it uses as much as digits as its factorization.

21970321 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10322.

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

The square root of 21970321 is about 4687.2509000479. The cubic root of 21970321 is about 280.0778737479.

The spelling of 21970321 in words is "twenty-one million, nine hundred seventy thousand, three hundred twenty-one".