21780018072 has 64 divisors (see below), whose sum is σ = 61247013600. Its totient is φ = 7260000192.

The previous prime is 21780018067. The next prime is 21780018089. The reversal of 21780018072 is 27081008712.

It is a happy number.

It is a hoax number, since the sum of its digits (36) coincides with the sum of the digits of its distinct prime factors.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 604933 + ... + 639924.

Almost surely, 2^21780018072 is an apocalyptic number.

It is an amenable number.

21780018072 is an abundant number, since it is smaller than the sum of its proper divisors (39466995528).

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

21780018072 is an equidigital number, since it uses as much as digits as its factorization.

21780018072 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1244884 (or 1244862 counting only the distinct ones).

The product of its (nonzero) digits is 12544, while the sum is 36.

The spelling of 21780018072 in words is "twenty-one billion, seven hundred eighty million, eighteen thousand, seventy-two".