21780387450 has 72 divisors (see below), whose sum is σ = 58539780000. Its totient is φ = 5805806880.

The previous prime is 21780387449. The next prime is 21780387457. The reversal of 21780387450 is 5478308712.

21780387450 is a `hidden beast` number, since 217 + 8 + 0 + 387 + 4 + 50 = 666.

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

It is a junction number, because it is equal to n+sod(n) for n = 21780387396 and 21780387405.

It is not an unprimeable number, because it can be changed into a prime (21780387457) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 1341481 + ... + 1357619.

It is an arithmetic number, because the mean of its divisors is an integer number (813052500).

Almost surely, 2^21780387450 is an apocalyptic number.

21780387450 is an abundant number, since it is smaller than the sum of its proper divisors (36759392550).

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

21780387450 is a wasteful number, since it uses less digits than its factorization.

21780387450 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 19156 (or 19148 counting only the distinct ones).

The product of its (nonzero) digits is 376320, while the sum is 45.

The spelling of 21780387450 in words is "twenty-one billion, seven hundred eighty million, three hundred eighty-seven thousand, four hundred fifty".