21001542021 has 12 divisors (see below), whose sum is σ = 30356202240. Its totient is φ = 13991501160.

The previous prime is 21001542019. The next prime is 21001542031. The reversal of 21001542021 is 12024510012.

21001542021 is a `hidden beast` number, since 2 + 100 + 1 + 542 + 0 + 21 = 666.

It is not a de Polignac number, because 21001542021 - 2¹ = 21001542019 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21001541985 and 21001542003.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21001542031) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 779931 + ... + 806408.

It is an arithmetic number, because the mean of its divisors is an integer number (2529683520).

Almost surely, 2^21001542021 is an apocalyptic number.

It is an amenable number.

21001542021 is a deficient number, since it is larger than the sum of its proper divisors (9354660219).

21001542021 is a wasteful number, since it uses less digits than its factorization.

21001542021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1587816 (or 1587813 counting only the distinct ones).

The product of its (nonzero) digits is 160, while the sum is 18.

The spelling of 21001542021 in words is "twenty-one billion, one million, five hundred forty-two thousand, twenty-one".