661237809 has 8 divisors (see below), whose sum is σ = 890380032. Its totient is φ = 436460400.

The previous prime is 661237799. The next prime is 661237817. The reversal of 661237809 is 908732166.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 661237809 - 2⁴ = 661237793 is a prime.

It is a super-2 number, since 2×661237809² = 874470880102240962, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (661237859) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1090849 + ... + 1091454.

It is an arithmetic number, because the mean of its divisors is an integer number (111297504).

Almost surely, 2^661237809 is an apocalyptic number.

It is an amenable number.

661237809 is a deficient number, since it is larger than the sum of its proper divisors (229142223).

661237809 is a wasteful number, since it uses less digits than its factorization.

661237809 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2182407.

The product of its (nonzero) digits is 108864, while the sum is 42.

The square root of 661237809 is about 25714.5446975053. The cubic root of 661237809 is about 871.2027268067.

The spelling of 661237809 in words is "six hundred sixty-one million, two hundred thirty-seven thousand, eight hundred nine".