21901181 has 4 divisors (see below), whose sum is σ = 22022364. Its totient is φ = 21780000.

The previous prime is 21901171. The next prime is 21901183. The reversal of 21901181 is 18110912.

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 4553956 + 17347225 = 2134^2 + 4165^2 .

It is a cyclic number.

It is not a de Polignac number, because 21901181 - 2¹⁰ = 21900157 is a prime.

It is a super-2 number, since 2×21901181² = 959323458389522, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21901183) 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, 60320 + ... + 60681.

It is an arithmetic number, because the mean of its divisors is an integer number (5505591).

Almost surely, 2^21901181 is an apocalyptic number.

It is an amenable number.

21901181 is a deficient number, since it is larger than the sum of its proper divisors (121183).

21901181 is a wasteful number, since it uses less digits than its factorization.

21901181 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 121182.

The product of its (nonzero) digits is 144, while the sum is 23.

The square root of 21901181 is about 4679.8697631451. The cubic root of 21901181 is about 279.7837658761.

It can be divided in two parts, 21901 and 181, that multiplied together give a square (3964081 = 1991²).

The spelling of 21901181 in words is "twenty-one million, nine hundred one thousand, one hundred eighty-one".