21426397 has 4 divisors (see below), whose sum is σ = 21436956. Its totient is φ = 21415840.

The previous prime is 21426371. The next prime is 21426401. The reversal of 21426397 is 79362412.

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 can be written as a sum of positive squares in 2 ways, for example, as 2013561 + 19412836 = 1419^2 + 4406^2 .

It is a cyclic number.

It is not a de Polignac number, because 21426397 - 2²³ = 13037789 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 (21426337) 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, 1168 + ... + 6649.

It is an arithmetic number, because the mean of its divisors is an integer number (5359239).

Almost surely, 2^21426397 is an apocalyptic number.

It is an amenable number.

21426397 is a deficient number, since it is larger than the sum of its proper divisors (10559).

21426397 is an equidigital number, since it uses as much as digits as its factorization.

21426397 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10558.

The product of its digits is 18144, while the sum is 34.

The square root of 21426397 is about 4628.8656277753. The cubic root of 21426397 is about 277.7472168630.

The spelling of 21426397 in words is "twenty-one million, four hundred twenty-six thousand, three hundred ninety-seven".