21372155 has 8 divisors (see below), whose sum is σ = 29310432. Its totient is φ = 14655168.

The previous prime is 21372151. The next prime is 21372157. The reversal of 21372155 is 55127312.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21372155 - 2² = 21372151 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21372151) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 305282 + ... + 305351.

It is an arithmetic number, because the mean of its divisors is an integer number (3663804).

Almost surely, 2^21372155 is an apocalyptic number.

21372155 is a deficient number, since it is larger than the sum of its proper divisors (7938277).

21372155 is an equidigital number, since it uses as much as digits as its factorization.

21372155 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 610645.

The product of its digits is 2100, while the sum is 26.

The square root of 21372155 is about 4623.0028120260. The cubic root of 21372155 is about 277.5126417962.

Subtracting from 21372155 its sum of digits (26), we obtain a square (21372129 = 4623²).

Adding to 21372155 its reverse (55127312), we get a palindrome (76499467).

The spelling of 21372155 in words is "twenty-one million, three hundred seventy-two thousand, one hundred fifty-five".