20981709 has 24 divisors (see below), whose sum is σ = 35485632. Its totient is φ = 11695680.

The previous prime is 20981677. The next prime is 20981711. The reversal of 20981709 is 90718902.

It is a happy number.

It is not a de Polignac number, because 20981709 - 2⁵ = 20981677 is a prime.

It is a super-2 number, since 2×20981709² = 880464225121362, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20981749) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 1479 + ... + 6644.

It is an arithmetic number, because the mean of its divisors is an integer number (1478568).

Almost surely, 2^20981709 is an apocalyptic number.

It is an amenable number.

20981709 is a deficient number, since it is larger than the sum of its proper divisors (14503923).

20981709 is a wasteful number, since it uses less digits than its factorization.

20981709 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8177 (or 8174 counting only the distinct ones).

The product of its (nonzero) digits is 9072, while the sum is 36.

The square root of 20981709 is about 4580.5795484851. The cubic root of 20981709 is about 275.8122936057.

It can be divided in two parts, 209 and 81709, that added together give a palindrome (81918).

The spelling of 20981709 in words is "twenty million, nine hundred eighty-one thousand, seven hundred nine".