21013155 has 16 divisors (see below), whose sum is σ = 37356960. Its totient is φ = 11206944.

The previous prime is 21013127. The next prime is 21013159. The reversal of 21013155 is 55131012.

It is not a de Polignac number, because 21013155 - 2¹⁵ = 20980387 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21013159) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 77692 + ... + 77961.

It is an arithmetic number, because the mean of its divisors is an integer number (2334810).

Almost surely, 2^21013155 is an apocalyptic number.

21013155 is a deficient number, since it is larger than the sum of its proper divisors (16343805).

21013155 is a wasteful number, since it uses less digits than its factorization.

21013155 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 155667 (or 155661 counting only the distinct ones).

The product of its (nonzero) digits is 150, while the sum is 18.

The square root of 21013155 is about 4584.0107984166. The cubic root of 21013155 is about 275.9500145773.

Adding to 21013155 its reverse (55131012), we get a palindrome (76144167).

The spelling of 21013155 in words is "twenty-one million, thirteen thousand, one hundred fifty-five".