661640430 has 64 divisors (see below), whose sum is σ = 1739750400. Its totient is φ = 159707520.

The previous prime is 661640407. The next prime is 661640431. The reversal of 661640430 is 34046166.

It is a super-2 number, since 2×661640430² = 875536117221169800, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (30).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (661640431) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 74676 + ... + 83064.

It is an arithmetic number, because the mean of its divisors is an integer number (27183600).

Almost surely, 2^661640430 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 661640430, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (869875200).

661640430 is an abundant number, since it is smaller than the sum of its proper divisors (1078109970).

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

661640430 is a wasteful number, since it uses less digits than its factorization.

661640430 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8649.

The product of its (nonzero) digits is 10368, while the sum is 30.

The square root of 661640430 is about 25722.3721689894. The cubic root of 661640430 is about 871.3795131006.

Adding to 661640430 its reverse (34046166), we get a palindrome (695686596).

The spelling of 661640430 in words is "six hundred sixty-one million, six hundred forty thousand, four hundred thirty".