20865521401 has 2 divisors, whose sum is σ = 20865521402. Its totient is φ = 20865521400.

The previous prime is 20865521389. The next prime is 20865521419. The reversal of 20865521401 is 10412556802.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 13075693801 + 7789827600 = 114349^2 + 88260^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20865521401 is a prime.

It is a super-3 number, since 3×20865521401³ (a number of 32 digits) contains 333 as substring.

It is not a weakly prime, because it can be changed into another prime (20865521701) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10432760700 + 10432760701.

It is an arithmetic number, because the mean of its divisors is an integer number (10432760701).

Almost surely, 2^20865521401 is an apocalyptic number.

It is an amenable number.

20865521401 is a deficient number, since it is larger than the sum of its proper divisors (1).

20865521401 is an equidigital number, since it uses as much as digits as its factorization.

20865521401 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 19200, while the sum is 34.

The spelling of 20865521401 in words is "twenty billion, eight hundred sixty-five million, five hundred twenty-one thousand, four hundred one".