21870899 has 4 divisors (see below), whose sum is σ = 21886536. Its totient is φ = 21855264.

The previous prime is 21870883. The next prime is 21870931. The reversal of 21870899 is 99807812.

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 21870899 - 2⁴ = 21870883 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21870809) 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, 5489 + ... + 8594.

It is an arithmetic number, because the mean of its divisors is an integer number (5471634).

Almost surely, 2^21870899 is an apocalyptic number.

21870899 is a deficient number, since it is larger than the sum of its proper divisors (15637).

21870899 is a wasteful number, since it uses less digits than its factorization.

21870899 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 15636.

The product of its (nonzero) digits is 72576, while the sum is 44.

The square root of 21870899 is about 4676.6332975764. The cubic root of 21870899 is about 279.6547573105.

It can be divided in two parts, 218 and 70899, that added together give a palindrome (71117).

The spelling of 21870899 in words is "twenty-one million, eight hundred seventy thousand, eight hundred ninety-nine".