21685870 has 8 divisors (see below), whose sum is σ = 39034584. Its totient is φ = 8674344.

The previous prime is 21685861. The next prime is 21685879. The reversal of 21685870 is 7858612.

It is an interprime number because it is at equal distance from previous prime (21685861) and next prime (21685879).

It is a sphenic number, since it is the product of 3 distinct primes.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21685879) 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, 1084284 + ... + 1084303.

It is an arithmetic number, because the mean of its divisors is an integer number (4879323).

Almost surely, 2^21685870 is an apocalyptic number.

21685870 is a deficient number, since it is larger than the sum of its proper divisors (17348714).

21685870 is a wasteful number, since it uses less digits than its factorization.

21685870 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2168594.

The product of its (nonzero) digits is 26880, while the sum is 37.

The square root of 21685870 is about 4656.8089932914. The cubic root of 21685870 is about 278.8638913367.

The spelling of 21685870 in words is "twenty-one million, six hundred eighty-five thousand, eight hundred seventy".