21820427 has 4 divisors (see below), whose sum is σ = 21841416. Its totient is φ = 21799440.

The previous prime is 21820423. The next prime is 21820429. The reversal of 21820427 is 72402812.

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 21820427 - 2² = 21820423 is a prime.

It is a super-2 number, since 2×21820427² = 952262068924658, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21820396 and 21820405.

It is not an unprimeable number, because it can be changed into a prime (21820423) 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, 8849 + ... + 11042.

It is an arithmetic number, because the mean of its divisors is an integer number (5460354).

Almost surely, 2^21820427 is an apocalyptic number.

21820427 is a deficient number, since it is larger than the sum of its proper divisors (20989).

21820427 is a wasteful number, since it uses less digits than its factorization.

21820427 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 20988.

The product of its (nonzero) digits is 1792, while the sum is 26.

The square root of 21820427 is about 4671.2339911420. The cubic root of 21820427 is about 279.4394696126.

The spelling of 21820427 in words is "twenty-one million, eight hundred twenty thousand, four hundred twenty-seven".