21510405125 has 16 divisors (see below), whose sum is σ = 29285440704. Its totient is φ = 15643930000.

The previous prime is 21510405109. The next prime is 21510405127. The reversal of 21510405125 is 52150401512.

It is not a de Polignac number, because 21510405125 - 2⁴ = 21510405109 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 21510405094 and 21510405103.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21510405127) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 7820591 + ... + 7823340.

It is an arithmetic number, because the mean of its divisors is an integer number (1830340044).

Almost surely, 2^21510405125 is an apocalyptic number.

21510405125 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21510405125 is a deficient number, since it is larger than the sum of its proper divisors (7775035579).

21510405125 is a wasteful number, since it uses less digits than its factorization.

21510405125 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 15643957 (or 15643947 counting only the distinct ones).

The product of its (nonzero) digits is 2000, while the sum is 26.

Adding to 21510405125 its reverse (52150401512), we get a palindrome (73660806637).

The spelling of 21510405125 in words is "twenty-one billion, five hundred ten million, four hundred five thousand, one hundred twenty-five".