21025421440 has 64 divisors (see below), whose sum is σ = 51087991320. Its totient is φ = 8272281600.

The previous prime is 21025421429. The next prime is 21025421441. The reversal of 21025421440 is 4412452012.

It can be written as a sum of positive squares in 4 ways, for example, as 5324329024 + 15701092416 = 72968^2 + 125304^2 .

It is a tau number, because it is divible by the number of its divisors (64).

It is a super-2 number, since 2×21025421440² (a number of 21 digits) contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21025421441) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 230241 + ... + 308320.

Almost surely, 2^21025421440 is an apocalyptic number.

21025421440 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21025421440 is an abundant number, since it is smaller than the sum of its proper divisors (30062569880).

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

21025421440 is an equidigital number, since it uses as much as digits as its factorization.

21025421440 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 538641 (or 538629 counting only the distinct ones).

The product of its (nonzero) digits is 2560, while the sum is 25.

Adding to 21025421440 its reverse (4412452012), we get a palindrome (25437873452).

The spelling of 21025421440 in words is "twenty-one billion, twenty-five million, four hundred twenty-one thousand, four hundred forty".