101218921 has 4 divisors (see below), whose sum is σ = 101239252. Its totient is φ = 101198592.

The previous prime is 101218919. The next prime is 101218979. The reversal of 101218921 is 129812101.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 72863296 + 28355625 = 8536^2 + 5325^2 .

It is a 3-Lehmer number, since φ(101218921) divides (101218921-1)³.

It is a cyclic number.

It is not a de Polignac number, because 101218921 - 2¹ = 101218919 is a prime.

It is an alternating number because its digits alternate between odd and even.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (101218991) 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, 2905 + ... + 14521.

It is an arithmetic number, because the mean of its divisors is an integer number (25309813).

It is a Poulet number, since it divides 2^101218920-1.

Almost surely, 2^101218921 is an apocalyptic number.

It is an amenable number.

101218921 is a deficient number, since it is larger than the sum of its proper divisors (20331).

101218921 is an equidigital number, since it uses as much as digits as its factorization.

101218921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 20330.

The product of its (nonzero) digits is 288, while the sum is 25.

The square root of 101218921 is about 10060.7614522957. The cubic root of 101218921 is about 466.0371822824.

The spelling of 101218921 in words is "one hundred one million, two hundred eighteen thousand, nine hundred twenty-one".