640644621554 has 16 divisors (see below), whose sum is σ = 1133675275776. Its totient is φ = 265705142400.

The previous prime is 640644621527. The next prime is 640644621559. The reversal of 640644621554 is 455126446046.

It is a super-2 number, since 2×640644621554² (a number of 24 digits) contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 640644621499 and 640644621508.

It is not an unprimeable number, because it can be changed into a prime (640644621559) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 738069407 + ... + 738070274.

It is an arithmetic number, because the mean of its divisors is an integer number (70854704736).

Almost surely, 2^640644621554 is an apocalyptic number.

640644621554 is a deficient number, since it is larger than the sum of its proper divisors (493030654222).

640644621554 is a wasteful number, since it uses less digits than its factorization.

640644621554 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1476139721.

The product of its (nonzero) digits is 2764800, while the sum is 47.

The spelling of 640644621554 in words is "six hundred forty billion, six hundred forty-four million, six hundred twenty-one thousand, five hundred fifty-four".