1661280390 has 576 divisors, whose sum is σ = 6055096320. Its totient is φ = 307929600.

The previous prime is 1661280367. The next prime is 1661280391. The reversal of 1661280390 is 930821661.

1661280390 is a `hidden beast` number, since 1 + 6 + 612 + 8 + 0 + 39 + 0 = 666.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1661280391) by changing a digit.

It is a polite number, since it can be written in 287 ways as a sum of consecutive naturals, for example, 44899452 + ... + 44899488.

It is an arithmetic number, because the mean of its divisors is an integer number (10512320).

Almost surely, 2^1661280390 is an apocalyptic number.

1661280390 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is a practical number, because each smaller number is the sum of distinct divisors of 1661280390, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (3027548160).

1661280390 is an abundant number, since it is smaller than the sum of its proper divisors (4393815930).

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

1661280390 is a wasteful number, since it uses less digits than its factorization.

1661280390 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 129 (or 115 counting only the distinct ones).

The product of its (nonzero) digits is 15552, while the sum is 36.

The square root of 1661280390 is about 40758.8075144502. The cubic root of 1661280390 is about 1184.3524956935.

Subtracting from 1661280390 its reverse (930821661), we obtain a square (730458729 = 27027²).

The spelling of 1661280390 in words is "one billion, six hundred sixty-one million, two hundred eighty thousand, three hundred ninety".