640121642 has 8 divisors (see below), whose sum is σ = 970971300. Its totient is φ = 316464544.

The previous prime is 640121641. The next prime is 640121663. The reversal of 640121642 is 246121046.

It can be written as a sum of positive squares in 2 ways, for example, as 616975921 + 23145721 = 24839^2 + 4811^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is not an unprimeable number, because it can be changed into a prime (640121641) 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, 1797917 + ... + 1798272.

Almost surely, 2^640121642 is an apocalyptic number.

640121642 is a deficient number, since it is larger than the sum of its proper divisors (330849658).

640121642 is a wasteful number, since it uses less digits than its factorization.

640121642 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3596280.

The product of its (nonzero) digits is 2304, while the sum is 26.

The square root of 640121642 is about 25300.6253282404. The cubic root of 640121642 is about 861.8284704175.

Adding to 640121642 its reverse (246121046), we get a palindrome (886242688).

The spelling of 640121642 in words is "six hundred forty million, one hundred twenty-one thousand, six hundred forty-two".