21557376021 has 8 divisors (see below), whose sum is σ = 28744013664. Its totient is φ = 14371161200.

The previous prime is 21557375993. The next prime is 21557376047. The reversal of 21557376021 is 12067375512.

It is a happy number.

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

It is a cyclic number.

It is not a de Polignac number, because 21557376021 - 2¹⁵ = 21557343253 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21557376521) 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, 43246 + ... + 212096.

It is an arithmetic number, because the mean of its divisors is an integer number (3593001708).

Almost surely, 2^21557376021 is an apocalyptic number.

It is an amenable number.

21557376021 is a deficient number, since it is larger than the sum of its proper divisors (7186637643).

21557376021 is a wasteful number, since it uses less digits than its factorization.

21557376021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 211411.

The product of its (nonzero) digits is 88200, while the sum is 39.

The spelling of 21557376021 in words is "twenty-one billion, five hundred fifty-seven million, three hundred seventy-six thousand, twenty-one".