21312873 has 6 divisors (see below), whose sum is σ = 30785274. Its totient is φ = 14208576.

The previous prime is 21312871. The next prime is 21312877. The reversal of 21312873 is 37821312.

It can be written as a sum of positive squares in only one way, i.e., 17040384 + 4272489 = 4128^2 + 2067^2 .

It is not a de Polignac number, because 21312873 - 2¹ = 21312871 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21312871) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1184040 + ... + 1184057.

It is an arithmetic number, because the mean of its divisors is an integer number (5130879).

Almost surely, 2^21312873 is an apocalyptic number.

It is an amenable number.

21312873 is a deficient number, since it is larger than the sum of its proper divisors (9472401).

21312873 is a wasteful number, since it uses less digits than its factorization.

21312873 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2368103 (or 2368100 counting only the distinct ones).

The product of its digits is 2016, while the sum is 27.

The square root of 21312873 is about 4616.5867261430. The cubic root of 21312873 is about 277.2558163621.

The spelling of 21312873 in words is "twenty-one million, three hundred twelve thousand, eight hundred seventy-three".