21397258 has 4 divisors (see below), whose sum is σ = 32095890. Its totient is φ = 10698628.

The previous prime is 21397253. The next prime is 21397279. The reversal of 21397258 is 85279312.

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., 14569489 + 6827769 = 3817^2 + 2613^2 .

It is not an unprimeable number, because it can be changed into a prime (21397253) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5349313 + ... + 5349316.

Almost surely, 2^21397258 is an apocalyptic number.

21397258 is a deficient number, since it is larger than the sum of its proper divisors (10698632).

21397258 is a wasteful number, since it uses less digits than its factorization.

21397258 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10698631.

The product of its digits is 30240, while the sum is 37.

The square root of 21397258 is about 4625.7170254999. The cubic root of 21397258 is about 277.6212515601.

The spelling of 21397258 in words is "twenty-one million, three hundred ninety-seven thousand, two hundred fifty-eight".