21778205404451 has 2 divisors, whose sum is σ = 21778205404452. Its totient is φ = 21778205404450.

The previous prime is 21778205404409. The next prime is 21778205404589. The reversal of 21778205404451 is 15440450287712.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21778205404451 - 2³⁸ = 21503327497507 is a prime.

It is a super-2 number, since 2×21778205404451² (a number of 27 digits) contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 21778205404451.

It is not a weakly prime, because it can be changed into another prime (21778205404651) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10889102702225 + 10889102702226.

It is an arithmetic number, because the mean of its divisors is an integer number (10889102702226).

Almost surely, 2^{21778205404451} is an apocalyptic number.

21778205404451 is a deficient number, since it is larger than the sum of its proper divisors (1).

21778205404451 is an equidigital number, since it uses as much as digits as its factorization.

21778205404451 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2508800, while the sum is 50.

The spelling of 21778205404451 in words is "twenty-one trillion, seven hundred seventy-eight billion, two hundred five million, four hundred four thousand, four hundred fifty-one".