20721021751 has 8 divisors (see below), whose sum is σ = 20835297360. Its totient is φ = 20606817792.

The previous prime is 20721021733. The next prime is 20721021773. The reversal of 20721021751 is 15712012702.

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 20721021751 - 2²¹ = 20718924599 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 (20721021851) 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, 625185 + ... + 657493.

It is an arithmetic number, because the mean of its divisors is an integer number (2604412170).

Almost surely, 2^20721021751 is an apocalyptic number.

20721021751 is a deficient number, since it is larger than the sum of its proper divisors (114275609).

20721021751 is a wasteful number, since it uses less digits than its factorization.

20721021751 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 35825.

The product of its (nonzero) digits is 1960, while the sum is 28.

The spelling of 20721021751 in words is "twenty billion, seven hundred twenty-one million, twenty-one thousand, seven hundred fifty-one".