21106858 has 4 divisors (see below), whose sum is σ = 31660290. Its totient is φ = 10553428.

The previous prime is 21106849. The next prime is 21106859. The reversal of 21106858 is 85860112.

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

It can be written as a sum of positive squares in only one way, i.e., 20675209 + 431649 = 4547^2 + 657^2 .

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is not an unprimeable number, because it can be changed into a prime (21106859) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5276713 + ... + 5276716.

Almost surely, 2^21106858 is an apocalyptic number.

21106858 is a deficient number, since it is larger than the sum of its proper divisors (10553432).

21106858 is a wasteful number, since it uses less digits than its factorization.

21106858 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10553431.

The product of its (nonzero) digits is 3840, while the sum is 31.

The square root of 21106858 is about 4594.2200643852. The cubic root of 21106858 is about 276.3595834772.

The spelling of 21106858 in words is "twenty-one million, one hundred six thousand, eight hundred fifty-eight".