21312020137 has 2 divisors, whose sum is σ = 21312020138. Its totient is φ = 21312020136.

The previous prime is 21312020101. The next prime is 21312020161. The reversal of 21312020137 is 73102021312.

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., 14813080681 + 6498939456 = 121709^2 + 80616^2 .

It is a cyclic number.

It is not a de Polignac number, because 21312020137 - 2¹¹ = 21312018089 is a prime.

It is a super-3 number, since 3×21312020137³ (a number of 32 digits) contains 333 as substring.

It is not a weakly prime, because it can be changed into another prime (21312030137) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10656010068 + 10656010069.

It is an arithmetic number, because the mean of its divisors is an integer number (10656010069).

Almost surely, 2^21312020137 is an apocalyptic number.

It is an amenable number.

21312020137 is a deficient number, since it is larger than the sum of its proper divisors (1).

21312020137 is an equidigital number, since it uses as much as digits as its factorization.

21312020137 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 504, while the sum is 22.

Adding to 21312020137 its reverse (73102021312), we get a palindrome (94414041449).

The spelling of 21312020137 in words is "twenty-one billion, three hundred twelve million, twenty thousand, one hundred thirty-seven".