20356721021 has 16 divisors (see below), whose sum is σ = 26143751424. Its totient is φ = 15406136064.

The previous prime is 20356720999. The next prime is 20356721039. The reversal of 20356721021 is 12012765302.

It is a happy number.

It is a cyclic number.

It is not a de Polignac number, because 20356721021 - 2¹⁴ = 20356704637 is a prime.

It is a super-3 number, since 3×20356721021³ (a number of 32 digits) contains 333 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20356721041) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 4860956 + ... + 4865141.

It is an arithmetic number, because the mean of its divisors is an integer number (1633984464).

Almost surely, 2^20356721021 is an apocalyptic number.

It is an amenable number.

20356721021 is a deficient number, since it is larger than the sum of its proper divisors (5787030403).

20356721021 is a wasteful number, since it uses less digits than its factorization.

20356721021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9726140.

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

The spelling of 20356721021 in words is "twenty billion, three hundred fifty-six million, seven hundred twenty-one thousand, twenty-one".