661161216 has 36 divisors (see below), whose sum is σ = 1759655072. Its totient is φ = 220386816.

The previous prime is 661161187. The next prime is 661161217. The reversal of 661161216 is 612161166.

It is a nude number because it is divisible by every one of its digits.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (661161217) 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, 429676 + ... + 431211.

Almost surely, 2^661161216 is an apocalyptic number.

It is an amenable number.

661161216 is an abundant number, since it is smaller than the sum of its proper divisors (1098493856).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

661161216 is an equidigital number, since it uses as much as digits as its factorization.

661161216 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 860906 (or 860892 counting only the distinct ones).

The product of its digits is 2592, while the sum is 30.

The square root of 661161216 is about 25713.0553610418. The cubic root of 661161216 is about 871.1690875693.

Subtracting from 661161216 its reverse (612161166), we obtain a triangular number (49000050 = T₉₈₉₉).

The spelling of 661161216 in words is "six hundred sixty-one million, one hundred sixty-one thousand, two hundred sixteen".