20766581 has 8 divisors (see below), whose sum is σ = 23436000. Its totient is φ = 18227440.

The previous prime is 20766533. The next prime is 20766593. The reversal of 20766581 is 18566702.

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

It is not a de Polignac number, because 20766581 - 2¹⁸ = 20504437 is a prime.

It is a super-2 number, since 2×20766581² = 862501772859122, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20766521) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 32231 + ... + 32868.

It is an arithmetic number, because the mean of its divisors is an integer number (2929500).

Almost surely, 2^20766581 is an apocalyptic number.

It is an amenable number.

20766581 is a deficient number, since it is larger than the sum of its proper divisors (2669419).

20766581 is a wasteful number, since it uses less digits than its factorization.

20766581 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 65139.

The product of its (nonzero) digits is 20160, while the sum is 35.

The square root of 20766581 is about 4557.0364273286. The cubic root of 20766581 is about 274.8664078401.

The spelling of 20766581 in words is "twenty million, seven hundred sixty-six thousand, five hundred eighty-one".