20722657 has 4 divisors (see below), whose sum is σ = 20733076. Its totient is φ = 20712240.

The previous prime is 20722649. The next prime is 20722661. The reversal of 20722657 is 75622702.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in 2 ways, for example, as 1852321 + 18870336 = 1361^2 + 4344^2 .

It is a cyclic number.

It is not a de Polignac number, because 20722657 - 2³ = 20722649 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20722687) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1194 + ... + 6547.

It is an arithmetic number, because the mean of its divisors is an integer number (5183269).

Almost surely, 2^20722657 is an apocalyptic number.

It is an amenable number.

20722657 is a deficient number, since it is larger than the sum of its proper divisors (10419).

20722657 is an equidigital number, since it uses as much as digits as its factorization.

20722657 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10418.

The product of its (nonzero) digits is 11760, while the sum is 31.

The square root of 20722657 is about 4552.2145160350. The cubic root of 20722657 is about 274.6724784002.

The spelling of 20722657 in words is "twenty million, seven hundred twenty-two thousand, six hundred fifty-seven".