21642561337 has 2 divisors, whose sum is σ = 21642561338. Its totient is φ = 21642561336.

The previous prime is 21642561299. The next prime is 21642561361. The reversal of 21642561337 is 73316524612.

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., 17102362176 + 4540199161 = 130776^2 + 67381^2 .

It is a cyclic number.

It is not a de Polignac number, because 21642561337 - 2¹⁹ = 21642037049 is a prime.

It is a super-2 number, since 2×21642561337² (a number of 21 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 21642561337.

It is not a weakly prime, because it can be changed into another prime (21642565337) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10821280668 + 10821280669.

It is an arithmetic number, because the mean of its divisors is an integer number (10821280669).

Almost surely, 2^21642561337 is an apocalyptic number.

It is an amenable number.

21642561337 is a deficient number, since it is larger than the sum of its proper divisors (1).

21642561337 is an equidigital number, since it uses as much as digits as its factorization.

21642561337 is an evil number, because the sum of its binary digits is even.

The product of its digits is 181440, while the sum is 40.

The spelling of 21642561337 in words is "twenty-one billion, six hundred forty-two million, five hundred sixty-one thousand, three hundred thirty-seven".