21125154021 has 8 divisors (see below), whose sum is σ = 28457252544. Its totient is φ = 13938245760.

The previous prime is 21125154007. The next prime is 21125154097. The reversal of 21125154021 is 12045152112.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21125154021 - 2⁹ = 21125153509 is a prime.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 21125153982 and 21125154000.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21125154821) 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, 36297225 + ... + 36297806.

It is an arithmetic number, because the mean of its divisors is an integer number (3557156568).

Almost surely, 2^21125154021 is an apocalyptic number.

It is an amenable number.

21125154021 is a deficient number, since it is larger than the sum of its proper divisors (7332098523).

21125154021 is an equidigital number, since it uses as much as digits as its factorization.

21125154021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 72595131.

The product of its (nonzero) digits is 800, while the sum is 24.

The spelling of 21125154021 in words is "twenty-one billion, one hundred twenty-five million, one hundred fifty-four thousand, twenty-one".