20979175681 has 2 divisors, whose sum is σ = 20979175682. Its totient is φ = 20979175680.

The previous prime is 20979175663. The next prime is 20979175687. The reversal of 20979175681 is 18657197902.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20962406656 + 16769025 = 144784^2 + 4095^2 .

It is a cyclic number.

It is not a de Polignac number, because 20979175681 - 2⁹ = 20979175169 is a prime.

It is a super-2 number, since 2×20979175681² (a number of 21 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (20979175687) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10489587840 + 10489587841.

It is an arithmetic number, because the mean of its divisors is an integer number (10489587841).

Almost surely, 2^20979175681 is an apocalyptic number.

It is an amenable number.

20979175681 is a deficient number, since it is larger than the sum of its proper divisors (1).

20979175681 is an equidigital number, since it uses as much as digits as its factorization.

20979175681 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1905120, while the sum is 55.

The spelling of 20979175681 in words is "twenty billion, nine hundred seventy-nine million, one hundred seventy-five thousand, six hundred eighty-one".