21399671 has 4 divisors (see below), whose sum is σ = 21414552. Its totient is φ = 21384792.

The previous prime is 21399661. The next prime is 21399689. The reversal of 21399671 is 17699312.

It is a happy number.

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 21399671 - 2¹⁰ = 21398647 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 (21399661) 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, 5021 + ... + 8246.

It is an arithmetic number, because the mean of its divisors is an integer number (5353638).

Almost surely, 2^21399671 is an apocalyptic number.

21399671 is a deficient number, since it is larger than the sum of its proper divisors (14881).

21399671 is a wasteful number, since it uses less digits than its factorization.

21399671 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 14880.

The product of its digits is 20412, while the sum is 38.

The square root of 21399671 is about 4625.9778425756. The cubic root of 21399671 is about 277.6316870857.

The spelling of 21399671 in words is "twenty-one million, three hundred ninety-nine thousand, six hundred seventy-one".