21421653640 has 32 divisors (see below), whose sum is σ = 48279240000. Its totient is φ = 8554346944.

The previous prime is 21421653629. The next prime is 21421653647. The reversal of 21421653640 is 4635612412.

It is a junction number, because it is equal to n+sod(n) for n = 21421653596 and 21421653605.

It is not an unprimeable number, because it can be changed into a prime (21421653647) by changing a digit.

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 7 ways as a sum of consecutive naturals, for example, 423070 + ... + 470989.

It is an arithmetic number, because the mean of its divisors is an integer number (1508726250).

Almost surely, 2^21421653640 is an apocalyptic number.

21421653640 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21421653640 is an abundant number, since it is smaller than the sum of its proper divisors (26857586360).

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

21421653640 is a wasteful number, since it uses less digits than its factorization.

21421653640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 894669 (or 894665 counting only the distinct ones).

The product of its (nonzero) digits is 34560, while the sum is 34.

The spelling of 21421653640 in words is "twenty-one billion, four hundred twenty-one million, six hundred fifty-three thousand, six hundred forty".