21512155411 has 4 divisors (see below), whose sum is σ = 21513265632. Its totient is φ = 21511045192.

The previous prime is 21512155391. The next prime is 21512155429. The reversal of 21512155411 is 11455121512.

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

It is a cyclic number.

It is not a de Polignac number, because 21512155411 - 2³³ = 12922220819 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21512155411.

It is not an unprimeable number, because it can be changed into a prime (21512155481) 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, 525520 + ... + 564973.

It is an arithmetic number, because the mean of its divisors is an integer number (5378316408).

Almost surely, 2^21512155411 is an apocalyptic number.

21512155411 is a deficient number, since it is larger than the sum of its proper divisors (1110221).

21512155411 is a wasteful number, since it uses less digits than its factorization.

21512155411 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1110220.

The product of its digits is 2000, while the sum is 28.

Adding to 21512155411 its reverse (11455121512), we get a palindrome (32967276923).

The spelling of 21512155411 in words is "twenty-one billion, five hundred twelve million, one hundred fifty-five thousand, four hundred eleven".