20721607 has 4 divisors (see below), whose sum is σ = 20754576. Its totient is φ = 20688640.

The previous prime is 20721599. The next prime is 20721611. The reversal of 20721607 is 70612702.

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

It is a cyclic number.

It is not a de Polignac number, because 20721607 - 2³ = 20721599 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20721637) 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, 15523 + ... + 16804.

It is an arithmetic number, because the mean of its divisors is an integer number (5188644).

Almost surely, 2^20721607 is an apocalyptic number.

20721607 is a deficient number, since it is larger than the sum of its proper divisors (32969).

20721607 is an equidigital number, since it uses as much as digits as its factorization.

20721607 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 32968.

The product of its (nonzero) digits is 1176, while the sum is 25.

The square root of 20721607 is about 4552.0991860899. The cubic root of 20721607 is about 274.6678391790.

The spelling of 20721607 in words is "twenty million, seven hundred twenty-one thousand, six hundred seven".