191221015 has 16 divisors (see below), whose sum is σ = 246596832. Its totient is φ = 141825024.

The previous prime is 191220949. The next prime is 191221033. The reversal of 191221015 is 510122191.

It is a cyclic number.

It is not a de Polignac number, because 191221015 - 2¹¹ = 191218967 is a prime.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 11094 + ... + 22483.

It is an arithmetic number, because the mean of its divisors is an integer number (15412302).

Almost surely, 2^191221015 is an apocalyptic number.

191221015 is a deficient number, since it is larger than the sum of its proper divisors (55375817).

191221015 is a wasteful number, since it uses less digits than its factorization.

191221015 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 33666.

The product of its (nonzero) digits is 180, while the sum is 22.

The square root of 191221015 is about 13828.2686913438. The cubic root of 191221015 is about 576.1185686580.

The spelling of 191221015 in words is "one hundred ninety-one million, two hundred twenty-one thousand, fifteen".