21090401640 has 864 divisors, whose sum is σ = 90152342280. Its totient is φ = 4257792000.

The previous prime is 21090401627. The next prime is 21090401659. The reversal of 21090401640 is 4610409012.

21090401640 is a `hidden beast` number, since 2 + 10 + 9 + 0 + 4 + 0 + 1 + 640 = 666.

It can be written as a sum of positive squares in 4 ways, for example, as 14097762756 + 6992638884 = 118734^2 + 83622^2 .

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 215 ways as a sum of consecutive naturals, for example, 87511920 + ... + 87512160.

Almost surely, 2^21090401640 is an apocalyptic number.

21090401640 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 21090401640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (45076171140).

21090401640 is an abundant number, since it is smaller than the sum of its proper divisors (69061940640).

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

21090401640 is a wasteful number, since it uses less digits than its factorization.

21090401640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 335 (or 310 counting only the distinct ones).

The product of its (nonzero) digits is 1728, while the sum is 27.

The spelling of 21090401640 in words is "twenty-one billion, ninety million, four hundred one thousand, six hundred forty".