21231901 has 4 divisors (see below), whose sum is σ = 21311100. Its totient is φ = 21152704.

The previous prime is 21231893. The next prime is 21231923. The reversal of 21231901 is 10913212.

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 11628100 + 9603801 = 3410^2 + 3099^2 .

It is a cyclic number.

It is not a de Polignac number, because 21231901 - 2³ = 21231893 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21231941) 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, 39196 + ... + 39733.

It is an arithmetic number, because the mean of its divisors is an integer number (5327775).

Almost surely, 2^21231901 is an apocalyptic number.

It is an amenable number.

21231901 is a deficient number, since it is larger than the sum of its proper divisors (79199).

21231901 is an equidigital number, since it uses as much as digits as its factorization.

21231901 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 79198.

The product of its (nonzero) digits is 108, while the sum is 19.

The square root of 21231901 is about 4607.8086982860. The cubic root of 21231901 is about 276.9042534234.

The spelling of 21231901 in words is "twenty-one million, two hundred thirty-one thousand, nine hundred one".