661427029440 has 336 divisors, whose sum is σ = 2460119755392. Its totient is φ = 162472624128.

The previous prime is 661427029433. The next prime is 661427029481. The reversal of 661427029440 is 44920724166.

661427029440 is a `hidden beast` number, since 6 + 614 + 2 + 7 + 0 + 29 + 4 + 4 + 0 = 666.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 2157402 + ... + 2444838.

Almost surely, 2^661427029440 is an apocalyptic number.

661427029440 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 661427029440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1230059877696).

661427029440 is an abundant number, since it is smaller than the sum of its proper divisors (1798692725952).

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

661427029440 is a wasteful number, since it uses less digits than its factorization.

661427029440 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 287524 (or 287511 counting only the distinct ones).

The product of its (nonzero) digits is 580608, while the sum is 45.

The spelling of 661427029440 in words is "six hundred sixty-one billion, four hundred twenty-seven million, twenty-nine thousand, four hundred forty".