21870061 has 4 divisors (see below), whose sum is σ = 22240800. Its totient is φ = 21499324.

The previous prime is 21870053. The next prime is 21870091. The reversal of 21870061 is 16007812.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21870061 - 2³ = 21870053 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21870011) 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, 185281 + ... + 185398.

It is an arithmetic number, because the mean of its divisors is an integer number (5560200).

Almost surely, 2^21870061 is an apocalyptic number.

It is an amenable number.

21870061 is a deficient number, since it is larger than the sum of its proper divisors (370739).

21870061 is an equidigital number, since it uses as much as digits as its factorization.

21870061 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 370738.

The product of its (nonzero) digits is 672, while the sum is 25.

The square root of 21870061 is about 4676.5437023511. The cubic root of 21870061 is about 279.6511855372.

Adding to 21870061 its reverse (16007812), we get a palindrome (37877873).

The spelling of 21870061 in words is "twenty-one million, eight hundred seventy thousand, sixty-one".