21397394 has 4 divisors (see below), whose sum is σ = 32096094. Its totient is φ = 10698696.

The previous prime is 21397393. The next prime is 21397421. The reversal of 21397394 is 49379312.

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

It can be written as a sum of positive squares in only one way, i.e., 20367169 + 1030225 = 4513^2 + 1015^2 .

It is not an unprimeable number, because it can be changed into a prime (21397391) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5349347 + ... + 5349350.

Almost surely, 2^21397394 is an apocalyptic number.

21397394 is a deficient number, since it is larger than the sum of its proper divisors (10698700).

21397394 is a wasteful number, since it uses less digits than its factorization.

21397394 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10698699.

The product of its digits is 40824, while the sum is 38.

The square root of 21397394 is about 4625.7317259002. The cubic root of 21397394 is about 277.6218397416.

The spelling of 21397394 in words is "twenty-one million, three hundred ninety-seven thousand, three hundred ninety-four".