20726561 has 8 divisors (see below), whose sum is σ = 21541800. Its totient is φ = 19918080.

The previous prime is 20726557. The next prime is 20726579. The reversal of 20726561 is 16562702.

It can be written as a sum of positive squares in 4 ways, for example, as 1638400 + 19088161 = 1280^2 + 4369^2 .

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

It is a cyclic number.

It is not a de Polignac number, because 20726561 - 2² = 20726557 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (29).

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20726501) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 5081 + ... + 8201.

It is an arithmetic number, because the mean of its divisors is an integer number (2692725).

Almost surely, 2^20726561 is an apocalyptic number.

It is an amenable number.

20726561 is a deficient number, since it is larger than the sum of its proper divisors (815239).

20726561 is a wasteful number, since it uses less digits than its factorization.

20726561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3379.

The product of its (nonzero) digits is 5040, while the sum is 29.

The square root of 20726561 is about 4552.6432981291. The cubic root of 20726561 is about 274.6897260924.

The spelling of 20726561 in words is "twenty million, seven hundred twenty-six thousand, five hundred sixty-one".