20721706 has 8 divisors (see below), whose sum is σ = 31102884. Its totient is φ = 10354080.

The previous prime is 20721683. The next prime is 20721713. The reversal of 20721706 is 60712702.

It can be written as a sum of positive squares in 2 ways, for example, as 20331081 + 390625 = 4509^2 + 625^2 .

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

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2446 + ... + 6886.

Almost surely, 2^20721706 is an apocalyptic number.

20721706 is a deficient number, since it is larger than the sum of its proper divisors (10381178).

20721706 is a wasteful number, since it uses less digits than its factorization.

20721706 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6776.

The product of its (nonzero) digits is 1176, while the sum is 25.

The square root of 20721706 is about 4552.1100601809. The cubic root of 20721706 is about 274.6682765980.

The spelling of 20721706 in words is "twenty million, seven hundred twenty-one thousand, seven hundred six".