5121651721 has 4 divisors (see below), whose sum is σ = 5198094352. Its totient is φ = 5045209092.

The previous prime is 5121651719. The next prime is 5121651739. The reversal of 5121651721 is 1271561215.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 5121651721 - 2¹ = 5121651719 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (5121651781) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 38221215 + ... + 38221348.

It is an arithmetic number, because the mean of its divisors is an integer number (1299523588).

Almost surely, 2^5121651721 is an apocalyptic number.

It is an amenable number.

5121651721 is a deficient number, since it is larger than the sum of its proper divisors (76442631).

5121651721 is an equidigital number, since it uses as much as digits as its factorization.

5121651721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 76442630.

The product of its digits is 4200, while the sum is 31.

The square root of 5121651721 is about 71565.7161006581. The cubic root of 5121651721 is about 1723.7330719436.

The spelling of 5121651721 in words is "five billion, one hundred twenty-one million, six hundred fifty-one thousand, seven hundred twenty-one".