215155391 has 4 divisors (see below), whose sum is σ = 234714984. Its totient is φ = 195595800.

The previous prime is 215155387. The next prime is 215155433. The reversal of 215155391 is 193551512.

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 215155391 - 2² = 215155387 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (215155891) 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, 9779780 + ... + 9779801.

It is an arithmetic number, because the mean of its divisors is an integer number (58678746).

Almost surely, 2^215155391 is an apocalyptic number.

215155391 is a deficient number, since it is larger than the sum of its proper divisors (19559593).

215155391 is a wasteful number, since it uses less digits than its factorization.

215155391 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 19559592.

The product of its digits is 6750, while the sum is 32.

The square root of 215155391 is about 14668.1761306578. The cubic root of 215155391 is about 599.2169330846.

The spelling of 215155391 in words is "two hundred fifteen million, one hundred fifty-five thousand, three hundred ninety-one".