21699847 has 4 divisors (see below), whose sum is σ = 23369080. Its totient is φ = 20030616.

The previous prime is 21699827. The next prime is 21699857. The reversal of 21699847 is 74899612.

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 21699847 - 2²³ = 13311239 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21699797 and 21699806.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21699817) 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, 834597 + ... + 834622.

It is an arithmetic number, because the mean of its divisors is an integer number (5842270).

Almost surely, 2^21699847 is an apocalyptic number.

21699847 is a deficient number, since it is larger than the sum of its proper divisors (1669233).

21699847 is a wasteful number, since it uses less digits than its factorization.

21699847 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1669232.

The product of its digits is 217728, while the sum is 46.

The square root of 21699847 is about 4658.3094573032. The cubic root of 21699847 is about 278.9237896873.

The spelling of 21699847 in words is "twenty-one million, six hundred ninety-nine thousand, eight hundred forty-seven".