21135747697 has 2 divisors, whose sum is σ = 21135747698. Its totient is φ = 21135747696.

The previous prime is 21135747667. The next prime is 21135747751. The reversal of 21135747697 is 79674753112.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 12626792161 + 8508955536 = 112369^2 + 92244^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21135747697 is a prime.

It is a super-2 number, since 2×21135747697² (a number of 21 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21135747667) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10567873848 + 10567873849.

It is an arithmetic number, because the mean of its divisors is an integer number (10567873849).

Almost surely, 2^21135747697 is an apocalyptic number.

It is an amenable number.

21135747697 is a deficient number, since it is larger than the sum of its proper divisors (1).

21135747697 is an equidigital number, since it uses as much as digits as its factorization.

21135747697 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2222640, while the sum is 52.

The spelling of 21135747697 in words is "twenty-one billion, one hundred thirty-five million, seven hundred forty-seven thousand, six hundred ninety-seven".