21577312021 has 2 divisors, whose sum is σ = 21577312022. Its totient is φ = 21577312020.

The previous prime is 21577312007. The next prime is 21577312049. The reversal of 21577312021 is 12021377512.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20111494225 + 1465817796 = 141815^2 + 38286^2 .

It is a cyclic number.

It is not a de Polignac number, because 21577312021 - 2²⁵ = 21543757589 is a prime.

It is a super-2 number, since 2×21577312021² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21577312051) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10788656010 + 10788656011.

It is an arithmetic number, because the mean of its divisors is an integer number (10788656011).

Almost surely, 2^21577312021 is an apocalyptic number.

It is an amenable number.

21577312021 is a deficient number, since it is larger than the sum of its proper divisors (1).

21577312021 is an equidigital number, since it uses as much as digits as its factorization.

21577312021 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 5880, while the sum is 31.

Adding to 21577312021 its reverse (12021377512), we get a palindrome (33598689533).

The spelling of 21577312021 in words is "twenty-one billion, five hundred seventy-seven million, three hundred twelve thousand, twenty-one".