21512155061 has 4 divisors (see below), whose sum is σ = 21556328352. Its totient is φ = 21467981772.

The previous prime is 21512155051. The next prime is 21512155073. The reversal of 21512155061 is 16055121512.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21512155061 - 2²² = 21507960757 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21512155051) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 22085915 + ... + 22086888.

It is an arithmetic number, because the mean of its divisors is an integer number (5389082088).

Almost surely, 2^21512155061 is an apocalyptic number.

It is an amenable number.

21512155061 is a deficient number, since it is larger than the sum of its proper divisors (44173291).

21512155061 is an equidigital number, since it uses as much as digits as its factorization.

21512155061 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 44173290.

The product of its (nonzero) digits is 3000, while the sum is 29.

Adding to 21512155061 its reverse (16055121512), we get a palindrome (37567276573).

The spelling of 21512155061 in words is "twenty-one billion, five hundred twelve million, one hundred fifty-five thousand, sixty-one".