1645387780 has 24 divisors (see below), whose sum is σ = 3548702808. Its totient is φ = 640366848.

The previous prime is 1645387771. The next prime is 1645387787. The reversal of 1645387780 is 877835461.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 796481284 + 848906496 = 28222^2 + 29136^2 .

It is not an unprimeable number, because it can be changed into a prime (1645387787) 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, 1111009 + ... + 1112488.

It is an arithmetic number, because the mean of its divisors is an integer number (147862617).

Almost surely, 2^1645387780 is an apocalyptic number.

1645387780 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

1645387780 is an abundant number, since it is smaller than the sum of its proper divisors (1903315028).

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

1645387780 is a wasteful number, since it uses less digits than its factorization.

1645387780 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2223543 (or 2223541 counting only the distinct ones).

The product of its (nonzero) digits is 1128960, while the sum is 49.

The square root of 1645387780 is about 40563.3797901506. The cubic root of 1645387780 is about 1180.5636921837.

The spelling of 1645387780 in words is "one billion, six hundred forty-five million, three hundred eighty-seven thousand, seven hundred eighty".