21012101531 has 4 divisors (see below), whose sum is σ = 21016122072. Its totient is φ = 21008080992.

The previous prime is 21012101497. The next prime is 21012101533. The reversal of 21012101531 is 13510121012.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21012101531 is a prime.

It is a super-2 number, since 2×21012101531² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21012101533) by changing a digit.

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 3 ways as a sum of consecutive naturals, for example, 2002421 + ... + 2012886.

It is an arithmetic number, because the mean of its divisors is an integer number (5254030518).

Almost surely, 2^21012101531 is an apocalyptic number.

21012101531 is a deficient number, since it is larger than the sum of its proper divisors (4020541).

21012101531 is an equidigital number, since it uses as much as digits as its factorization.

21012101531 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4020540.

The product of its (nonzero) digits is 60, while the sum is 17.

Adding to 21012101531 its reverse (13510121012), we get a palindrome (34522222543).

The spelling of 21012101531 in words is "twenty-one billion, twelve million, one hundred one thousand, five hundred thirty-one".