21125105400 has 144 divisors (see below), whose sum is σ = 76179822840. Its totient is φ = 4828588800.

The previous prime is 21125105321. The next prime is 21125105429. The reversal of 21125105400 is 450152112.

It is a super-2 number, since 2×21125105400² (a number of 21 digits) contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (21).

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 35 ways as a sum of consecutive naturals, for example, 329871 + ... + 388670.

Almost surely, 2^21125105400 is an apocalyptic number.

21125105400 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21125105400 is an abundant number, since it is smaller than the sum of its proper divisors (55054717440).

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

21125105400 is a wasteful number, since it uses less digits than its factorization.

21125105400 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 718574 (or 718558 counting only the distinct ones).

The product of its (nonzero) digits is 400, while the sum is 21.

Adding to 21125105400 its reverse (450152112), we get a palindrome (21575257512).

The spelling of 21125105400 in words is "twenty-one billion, one hundred twenty-five million, one hundred five thousand, four hundred".