407721661 has 2 divisors, whose sum is σ = 407721662. Its totient is φ = 407721660.

The previous prime is 407721623. The next prime is 407721719. The reversal of 407721661 is 166127704.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 407272761 + 448900 = 20181^2 + 670^2 .

It is a cyclic number.

It is not a de Polignac number, because 407721661 - 2⁷ = 407721533 is a prime.

It is a super-3 number, since 3×407721661³ (a number of 27 digits) contains 333 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (407724661) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 203860830 + 203860831.

It is an arithmetic number, because the mean of its divisors is an integer number (203860831).

Almost surely, 2^407721661 is an apocalyptic number.

It is an amenable number.

407721661 is a deficient number, since it is larger than the sum of its proper divisors (1).

407721661 is an equidigital number, since it uses as much as digits as its factorization.

407721661 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 14112, while the sum is 34.

The square root of 407721661 is about 20192.1187843178. The cubic root of 407721661 is about 741.5172552509.

The spelling of 407721661 in words is "four hundred seven million, seven hundred twenty-one thousand, six hundred sixty-one".