921720155 has 8 divisors (see below), whose sum is σ = 1106594592. Its totient is φ = 737022528.

The previous prime is 921720131. The next prime is 921720167. The reversal of 921720155 is 551027129.

It is a happy number.

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 921720155 - 2⁶ = 921720091 is a prime.

It is a Duffinian number.

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 7 ways as a sum of consecutive naturals, for example, 32447 + ... + 53816.

It is an arithmetic number, because the mean of its divisors is an integer number (138324324).

Almost surely, 2^921720155 is an apocalyptic number.

921720155 is a deficient number, since it is larger than the sum of its proper divisors (184874437).

921720155 is a wasteful number, since it uses less digits than its factorization.

921720155 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 88405.

The product of its (nonzero) digits is 6300, while the sum is 32.

The square root of 921720155 is about 30359.8444495356. The cubic root of 921720155 is about 973.1946095246.

The spelling of 921720155 in words is "nine hundred twenty-one million, seven hundred twenty thousand, one hundred fifty-five".