66431261 has 4 divisors (see below), whose sum is σ = 71541372. Its totient is φ = 61321152.

The previous prime is 66431219. The next prime is 66431263. The reversal of 66431261 is 16213466.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 17347225 + 49084036 = 4165^2 + 7006^2 .

It is a cyclic number.

It is not a de Polignac number, because 66431261 - 2¹⁴ = 66414877 is a prime.

It is a super-2 number, since 2×66431261² = 8826224876100242, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66431263) 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, 2555036 + ... + 2555061.

It is an arithmetic number, because the mean of its divisors is an integer number (17885343).

Almost surely, 2^66431261 is an apocalyptic number.

It is an amenable number.

66431261 is a deficient number, since it is larger than the sum of its proper divisors (5110111).

66431261 is a wasteful number, since it uses less digits than its factorization.

66431261 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5110110.

The product of its digits is 5184, while the sum is 29.

The square root of 66431261 is about 8150.5374669404. The cubic root of 66431261 is about 405.0023085780.

The spelling of 66431261 in words is "sixty-six million, four hundred thirty-one thousand, two hundred sixty-one".