21870156 has 48 divisors (see below), whose sum is σ = 63624960. Its totient is φ = 5680320.

The previous prime is 21870131. The next prime is 21870161. The reversal of 21870156 is 65107812.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 10911 + ... + 12758.

It is an arithmetic number, because the mean of its divisors is an integer number (1325520).

Almost surely, 2^21870156 is an apocalyptic number.

It is an amenable number.

21870156 is an abundant number, since it is smaller than the sum of its proper divisors (41754804).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21870156 is a wasteful number, since it uses less digits than its factorization.

21870156 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 23694 (or 23692 counting only the distinct ones).

The product of its (nonzero) digits is 3360, while the sum is 30.

The square root of 21870156 is about 4676.5538594140. The cubic root of 21870156 is about 279.6515904564.

Adding to 21870156 its reverse (65107812), we get a palindrome (86977968).

The spelling of 21870156 in words is "twenty-one million, eight hundred seventy thousand, one hundred fifty-six".