641978091 has 24 divisors (see below), whose sum is σ = 951737696. Its totient is φ = 416845440.

The previous prime is 641978087. The next prime is 641978111. The reversal of 641978091 is 190879146.

It is a happy number.

It is not a de Polignac number, because 641978091 - 2² = 641978087 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (641978591) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 50871 + ... + 62223.

Almost surely, 2^641978091 is an apocalyptic number.

641978091 is a gapful number since it is divisible by the number (61) formed by its first and last digit.

641978091 is a deficient number, since it is larger than the sum of its proper divisors (309759605).

641978091 is a wasteful number, since it uses less digits than its factorization.

641978091 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11523 (or 11520 counting only the distinct ones).

The product of its (nonzero) digits is 108864, while the sum is 45.

The square root of 641978091 is about 25337.2865753221. The cubic root of 641978091 is about 862.6608103432.

The spelling of 641978091 in words is "six hundred forty-one million, nine hundred seventy-eight thousand, ninety-one".