5665840721 has 2 divisors, whose sum is σ = 5665840722. Its totient is φ = 5665840720.

The previous prime is 5665840681. The next prime is 5665840759. The reversal of 5665840721 is 1270485665.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 5547270400 + 118570321 = 74480^2 + 10889^2 .

It is a cyclic number.

It is not a de Polignac number, because 5665840721 - 2⁶ = 5665840657 is a prime.

It is not a weakly prime, because it can be changed into another prime (5665845721) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2832920360 + 2832920361.

It is an arithmetic number, because the mean of its divisors is an integer number (2832920361).

Almost surely, 2^5665840721 is an apocalyptic number.

It is an amenable number.

5665840721 is a deficient number, since it is larger than the sum of its proper divisors (1).

5665840721 is an equidigital number, since it uses as much as digits as its factorization.

5665840721 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 403200, while the sum is 44.

The square root of 5665840721 is about 75271.7790476617. The cubic root of 5665840721 is about 1782.7404574808.

It can be divided in two parts, 56658 and 40721, that added together give a palindrome (97379).

The spelling of 5665840721 in words is "five billion, six hundred sixty-five million, eight hundred forty thousand, seven hundred twenty-one".