661267091 has 4 divisors (see below), whose sum is σ = 670580784. Its totient is φ = 651953400.

The previous prime is 661267001. The next prime is 661267109. The reversal of 661267091 is 190762166.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-661267091 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (661267001) 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, 4656740 + ... + 4656881.

It is an arithmetic number, because the mean of its divisors is an integer number (167645196).

Almost surely, 2^661267091 is an apocalyptic number.

661267091 is a deficient number, since it is larger than the sum of its proper divisors (9313693).

661267091 is an equidigital number, since it uses as much as digits as its factorization.

661267091 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9313692.

The product of its (nonzero) digits is 27216, while the sum is 38.

The square root of 661267091 is about 25715.1140576899. The cubic root of 661267091 is about 871.2155866187.

The spelling of 661267091 in words is "six hundred sixty-one million, two hundred sixty-seven thousand, ninety-one".