21651780326400 has 1584 divisors, whose sum is σ = 93842120386560. Its totient is φ = 4659329433600.

The previous prime is 21651780326327. The next prime is 21651780326413. The reversal of 21651780326400 is 462308715612.

21651780326400 is a `hidden beast` number, since 2 + 16 + 517 + 80 + 3 + 2 + 6 + 40 + 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 143 ways as a sum of consecutive naturals, for example, 5117412285 + ... + 5117416515.

Almost surely, 2^{21651780326400} is an apocalyptic number.

21651780326400 is a gapful number since it is divisible by the number (20) 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 21651780326400, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (46921060193280).

21651780326400 is an abundant number, since it is smaller than the sum of its proper divisors (72190340060160).

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

21651780326400 is a wasteful number, since it uses less digits than its factorization.

21651780326400 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4460 (or 4434 counting only the distinct ones).

The product of its (nonzero) digits is 483840, while the sum is 45.

The spelling of 21651780326400 in words is "twenty-one trillion, six hundred fifty-one billion, seven hundred eighty million, three hundred twenty-six thousand, four hundred".