21165706 has 4 divisors (see below), whose sum is σ = 31748562. Its totient is φ = 10582852.

The previous prime is 21165671. The next prime is 21165733. The reversal of 21165706 is 60756112.

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., 19580625 + 1585081 = 4425^2 + 1259^2 .

It is a super-2 number, since 2×21165706² = 895974220956872, which contains 22 as substring.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5291425 + ... + 5291428.

Almost surely, 2^21165706 is an apocalyptic number.

21165706 is a deficient number, since it is larger than the sum of its proper divisors (10582856).

21165706 is a wasteful number, since it uses less digits than its factorization.

21165706 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10582855.

The product of its (nonzero) digits is 2520, while the sum is 28.

The square root of 21165706 is about 4600.6201755850. The cubic root of 21165706 is about 276.6161843990.

The spelling of 21165706 in words is "twenty-one million, one hundred sixty-five thousand, seven hundred six".