641554661 has 4 divisors (see below), whose sum is σ = 699877824. Its totient is φ = 583231500.

The previous prime is 641554657. The next prime is 641554673. The reversal of 641554661 is 166455146.

It is a happy number.

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 641554661 - 2² = 641554657 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (641554601) 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, 29161565 + ... + 29161586.

It is an arithmetic number, because the mean of its divisors is an integer number (174969456).

Almost surely, 2^641554661 is an apocalyptic number.

It is an amenable number.

641554661 is a deficient number, since it is larger than the sum of its proper divisors (58323163).

641554661 is a wasteful number, since it uses less digits than its factorization.

641554661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 58323162.

The product of its digits is 86400, while the sum is 38.

The square root of 641554661 is about 25328.9293299184. The cubic root of 641554661 is about 862.4711066705.

The spelling of 641554661 in words is "six hundred forty-one million, five hundred fifty-four thousand, six hundred sixty-one".