643532651551 has 16 divisors (see below), whose sum is σ = 650612239200. Its totient is φ = 636498570240.

The previous prime is 643532651497. The next prime is 643532651609. The reversal of 643532651551 is 155156235346.

It is a cyclic number.

It is not a de Polignac number, because 643532651551 - 2¹⁵ = 643532618783 is a prime.

It is a super-2 number, since 2×643532651551² (a number of 24 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (643532651651) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 29627271 + ... + 29648983.

It is an arithmetic number, because the mean of its divisors is an integer number (40663264950).

Almost surely, 2^643532651551 is an apocalyptic number.

643532651551 is a deficient number, since it is larger than the sum of its proper divisors (7079587649).

643532651551 is a wasteful number, since it uses less digits than its factorization.

643532651551 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 22746.

The product of its digits is 1620000, while the sum is 46.

Adding to 643532651551 its reverse (155156235346), we get a palindrome (798688886897).

It can be divided in two parts, 64353 and 2651551, that added together give a square (2715904 = 1648²).

The spelling of 643532651551 in words is "six hundred forty-three billion, five hundred thirty-two million, six hundred fifty-one thousand, five hundred fifty-one".