651551656521 has 4 divisors (see below), whose sum is σ = 868735542032. Its totient is φ = 434367771012.

The previous prime is 651551656453. The next prime is 651551656523. The reversal of 651551656521 is 125656155156.

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 not a de Polignac number, because 651551656521 - 2⁹ = 651551656009 is a prime.

It is a super-2 number, since 2×651551656521² (a number of 24 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (651551656523) 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, 108591942751 + ... + 108591942756.

It is an arithmetic number, because the mean of its divisors is an integer number (217183885508).

Almost surely, 2^651551656521 is an apocalyptic number.

It is an amenable number.

651551656521 is a deficient number, since it is larger than the sum of its proper divisors (217183885511).

651551656521 is a wasteful number, since it uses less digits than its factorization.

651551656521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 217183885510.

The product of its digits is 1350000, while the sum is 48.

The spelling of 651551656521 in words is "six hundred fifty-one billion, five hundred fifty-one million, six hundred fifty-six thousand, five hundred twenty-one".