21019018777 has 4 divisors (see below), whose sum is σ = 21053085876. Its totient is φ = 20984951680.

The previous prime is 21019018723. The next prime is 21019018843. The reversal of 21019018777 is 77781091012.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 5180544576 + 15838474201 = 71976^2 + 125851^2 .

It is a cyclic number.

It is not a de Polignac number, because 21019018777 - 2¹¹ = 21019016729 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21019048777) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 17032624 + ... + 17033857.

It is an arithmetic number, because the mean of its divisors is an integer number (5263271469).

Almost surely, 2^21019018777 is an apocalyptic number.

It is an amenable number.

21019018777 is a deficient number, since it is larger than the sum of its proper divisors (34067099).

21019018777 is an equidigital number, since it uses as much as digits as its factorization.

21019018777 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 34067098.

The product of its (nonzero) digits is 49392, while the sum is 43.

The spelling of 21019018777 in words is "twenty-one billion, nineteen million, eighteen thousand, seven hundred seventy-seven".