21207023155 has 16 divisors (see below), whose sum is σ = 27172442880. Its totient is φ = 15850584288.

The previous prime is 21207023143. The next prime is 21207023161. The reversal of 21207023155 is 55132070212.

It is a cyclic number.

It is not a de Polignac number, because 21207023155 - 2¹¹ = 21207021107 is a prime.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 2139345 + ... + 2149234.

It is an arithmetic number, because the mean of its divisors is an integer number (1698277680).

Almost surely, 2^21207023155 is an apocalyptic number.

21207023155 is a deficient number, since it is larger than the sum of its proper divisors (5965419725).

21207023155 is a wasteful number, since it uses less digits than its factorization.

21207023155 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4288650.

The product of its (nonzero) digits is 4200, while the sum is 28.

Adding to 21207023155 its reverse (55132070212), we get a palindrome (76339093367).

It can be divided in two parts, 212070 and 23155, that added together give a square (235225 = 485²).

The spelling of 21207023155 in words is "twenty-one billion, two hundred seven million, twenty-three thousand, one hundred fifty-five".