21398407 has 4 divisors (see below), whose sum is σ = 21444696. Its totient is φ = 21352120.

The previous prime is 21398381. The next prime is 21398413. The reversal of 21398407 is 70489312.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21398407 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 (21398437) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 22444 + ... + 23377.

It is an arithmetic number, because the mean of its divisors is an integer number (5361174).

Almost surely, 2^21398407 is an apocalyptic number.

21398407 is a deficient number, since it is larger than the sum of its proper divisors (46289).

21398407 is an equidigital number, since it uses as much as digits as its factorization.

21398407 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 46288.

The product of its (nonzero) digits is 12096, while the sum is 34.

The square root of 21398407 is about 4625.8412207943. The cubic root of 21398407 is about 277.6262207499.

The spelling of 21398407 in words is "twenty-one million, three hundred ninety-eight thousand, four hundred seven".