20720729 has 4 divisors (see below), whose sum is σ = 20840676. Its totient is φ = 20600784.

The previous prime is 20720719. The next prime is 20720731. The reversal of 20720729 is 92702702.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 18835600 + 1885129 = 4340^2 + 1373^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20720729 is a prime.

It is a super-2 number, since 2×20720729² = 858697220582882, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (20720719) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 59714 + ... + 60059.

It is an arithmetic number, because the mean of its divisors is an integer number (5210169).

Almost surely, 2^20720729 is an apocalyptic number.

It is an amenable number.

20720729 is a deficient number, since it is larger than the sum of its proper divisors (119947).

20720729 is a wasteful number, since it uses less digits than its factorization.

20720729 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 119946.

The product of its (nonzero) digits is 3528, while the sum is 29.

The square root of 20720729 is about 4552.0027460449. The cubic root of 20720729 is about 274.6639597860.

The spelling of 20720729 in words is "twenty million, seven hundred twenty thousand, seven hundred twenty-nine".