21900061 has 4 divisors (see below), whose sum is σ = 21912192. Its totient is φ = 21887932.

The previous prime is 21900059. The next prime is 21900091. The reversal of 21900061 is 16000912.

It is the 1911-st star number.

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, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 21900061 - 2¹ = 21900059 is a prime.

It is a super-2 number, since 2×21900061² = 959225343607442, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21900031) by changing a digit.

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 3 ways as a sum of consecutive naturals, for example, 2755 + ... + 7168.

It is an arithmetic number, because the mean of its divisors is an integer number (5478048).

Almost surely, 2^21900061 is an apocalyptic number.

It is an amenable number.

21900061 is a deficient number, since it is larger than the sum of its proper divisors (12131).

21900061 is an equidigital number, since it uses as much as digits as its factorization.

21900061 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12130.

The product of its (nonzero) digits is 108, while the sum is 19.

The square root of 21900061 is about 4679.7501001656. The cubic root of 21900061 is about 279.7789965266.

Adding to 21900061 its reverse (16000912), we get a palindrome (37900973).

The spelling of 21900061 in words is "twenty-one million, nine hundred thousand, sixty-one".