66401631 has 12 divisors (see below), whose sum is σ = 95993352. Its totient is φ = 44230896.

The previous prime is 66401617. The next prime is 66401639. The reversal of 66401631 is 13610466.

66401631 is a `hidden beast` number, since 6 + 640 + 16 + 3 + 1 = 666.

It is not a de Polignac number, because 66401631 - 2⁹ = 66401119 is a prime.

It is a super-2 number, since 2×66401631² = 8818353198920322, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 66401595 and 66401604.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66401639) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 12480 + ... + 16986.

It is an arithmetic number, because the mean of its divisors is an integer number (7999446).

Almost surely, 2^66401631 is an apocalyptic number.

66401631 is a deficient number, since it is larger than the sum of its proper divisors (29591721).

66401631 is a wasteful number, since it uses less digits than its factorization.

66401631 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6150 (or 6147 counting only the distinct ones).

The product of its (nonzero) digits is 2592, while the sum is 27.

The square root of 66401631 is about 8148.7195926722. The cubic root of 66401631 is about 404.9420859118.

The spelling of 66401631 in words is "sixty-six million, four hundred one thousand, six hundred thirty-one".