21398807 has 4 divisors (see below), whose sum is σ = 22525080. Its totient is φ = 20272536.

The previous prime is 21398791. The next prime is 21398813. The reversal of 21398807 is 70889312.

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

It is a cyclic number.

It is not a de Polignac number, because 21398807 - 2⁴ = 21398791 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 (21398827) 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, 563108 + ... + 563145.

It is an arithmetic number, because the mean of its divisors is an integer number (5631270).

Almost surely, 2^21398807 is an apocalyptic number.

21398807 is a deficient number, since it is larger than the sum of its proper divisors (1126273).

21398807 is a wasteful number, since it uses less digits than its factorization.

21398807 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1126272.

The product of its (nonzero) digits is 24192, while the sum is 38.

The square root of 21398807 is about 4625.8844559716. The cubic root of 21398807 is about 277.6279506263.

The spelling of 21398807 in words is "twenty-one million, three hundred ninety-eight thousand, eight hundred seven".