21630139 has 4 divisors (see below), whose sum is σ = 21704256. Its totient is φ = 21556024.

The previous prime is 21630131. The next prime is 21630179. The reversal of 21630139 is 93103612.

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

It is a cyclic number.

It is not a de Polignac number, because 21630139 - 2³ = 21630131 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21630131) 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, 36619 + ... + 37204.

It is an arithmetic number, because the mean of its divisors is an integer number (5426064).

Almost surely, 2^21630139 is an apocalyptic number.

21630139 is a deficient number, since it is larger than the sum of its proper divisors (74117).

21630139 is an equidigital number, since it uses as much as digits as its factorization.

21630139 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 74116.

The product of its (nonzero) digits is 972, while the sum is 25.

The square root of 21630139 is about 4650.8213253145. The cubic root of 21630139 is about 278.6248002306.

The spelling of 21630139 in words is "twenty-one million, six hundred thirty thousand, one hundred thirty-nine".