64161781 has 2 divisors, whose sum is σ = 64161782. Its totient is φ = 64161780.

The previous prime is 64161709. The next prime is 64161793. The reversal of 64161781 is 18716146.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 64160100 + 1681 = 8010^2 + 41^2 .

It is a cyclic number.

It is not a de Polignac number, because 64161781 - 2⁷ = 64161653 is a prime.

It is a super-2 number, since 2×64161781² = 8233468282183922, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (64162781) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 32080890 + 32080891.

It is an arithmetic number, because the mean of its divisors is an integer number (32080891).

Almost surely, 2^64161781 is an apocalyptic number.

It is an amenable number.

64161781 is a deficient number, since it is larger than the sum of its proper divisors (1).

64161781 is an equidigital number, since it uses as much as digits as its factorization.

64161781 is an evil number, because the sum of its binary digits is even.

The product of its digits is 8064, while the sum is 34.

The square root of 64161781 is about 8010.1049306485. The cubic root of 64161781 is about 400.3367601519.

The spelling of 64161781 in words is "sixty-four million, one hundred sixty-one thousand, seven hundred eighty-one".