661639037 has 4 divisors (see below), whose sum is σ = 668460156. Its totient is φ = 654817920.

The previous prime is 661639021. The next prime is 661639049. The reversal of 661639037 is 730936166.

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 152053561 + 509585476 = 12331^2 + 22574^2 .

It is a cyclic number.

It is not a de Polignac number, because 661639037 - 2⁴ = 661639021 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 661638985 and 661639003.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (661639007) 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, 3410414 + ... + 3410607.

It is an arithmetic number, because the mean of its divisors is an integer number (167115039).

Almost surely, 2^661639037 is an apocalyptic number.

It is an amenable number.

661639037 is a deficient number, since it is larger than the sum of its proper divisors (6821119).

661639037 is an equidigital number, since it uses as much as digits as its factorization.

661639037 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6821118.

The product of its (nonzero) digits is 122472, while the sum is 41.

The square root of 661639037 is about 25722.3450913792. The cubic root of 661639037 is about 871.3789015738.

The spelling of 661639037 in words is "six hundred sixty-one million, six hundred thirty-nine thousand, thirty-seven".