644378011 has 2 divisors, whose sum is σ = 644378012. Its totient is φ = 644378010.

The previous prime is 644377973. The next prime is 644378023. The reversal of 644378011 is 110873446.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 644378011 - 2¹⁹ = 643853723 is a prime.

It is a super-2 number, since 2×644378011² = 830446042120632242, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (644378041) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322189005 + 322189006.

It is an arithmetic number, because the mean of its divisors is an integer number (322189006).

Almost surely, 2^644378011 is an apocalyptic number.

644378011 is a deficient number, since it is larger than the sum of its proper divisors (1).

644378011 is an equidigital number, since it uses as much as digits as its factorization.

644378011 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 16128, while the sum is 34.

The square root of 644378011 is about 25384.6018483647. The cubic root of 644378011 is about 863.7344411879.

The spelling of 644378011 in words is "six hundred forty-four million, three hundred seventy-eight thousand, eleven".