21059661 has 12 divisors (see below), whose sum is σ = 32664192. Its totient is φ = 12034008.

The previous prime is 21059629. The next prime is 21059669. The reversal of 21059661 is 16695012.

It is not a de Polignac number, because 21059661 - 2⁵ = 21059629 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21059669) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 71485 + ... + 71778.

It is an arithmetic number, because the mean of its divisors is an integer number (2722016).

Almost surely, 2^21059661 is an apocalyptic number.

21059661 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

21059661 is a deficient number, since it is larger than the sum of its proper divisors (11604531).

21059661 is a wasteful number, since it uses less digits than its factorization.

21059661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 143280 (or 143273 counting only the distinct ones).

The product of its (nonzero) digits is 3240, while the sum is 30.

The square root of 21059661 is about 4589.0806268794. The cubic root of 21059661 is about 276.1534407246.

The spelling of 21059661 in words is "twenty-one million, fifty-nine thousand, six hundred sixty-one".