21391101 has 8 divisors (see below), whose sum is σ = 31690560. Its totient is φ = 14260716.

The previous prime is 21391091. The next prime is 21391129. The reversal of 21391101 is 10119312.

It is not a de Polignac number, because 21391101 - 2¹⁸ = 21128957 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21391301) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 396105 + ... + 396158.

It is an arithmetic number, because the mean of its divisors is an integer number (3961320).

Almost surely, 2^21391101 is an apocalyptic number.

It is an amenable number.

21391101 is a deficient number, since it is larger than the sum of its proper divisors (10299459).

21391101 is an equidigital number, since it uses as much as digits as its factorization.

21391101 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 792272 (or 792266 counting only the distinct ones).

The product of its (nonzero) digits is 54, while the sum is 18.

The square root of 21391101 is about 4625.0514591732. The cubic root of 21391101 is about 277.5946207644.

It can be divided in two parts, 2139 and 1101, that added together give a triangular number (3240 = T₈₀).

The spelling of 21391101 in words is "twenty-one million, three hundred ninety-one thousand, one hundred one".