21437661 has 8 divisors (see below), whose sum is σ = 32666944. Its totient is φ = 12250080.

The previous prime is 21437639. The next prime is 21437701. The reversal of 21437661 is 16673412.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21437661 - 2¹⁰ = 21436637 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21437161) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 510400 + ... + 510441.

It is an arithmetic number, because the mean of its divisors is an integer number (4083368).

Almost surely, 2^21437661 is an apocalyptic number.

21437661 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

21437661 is a deficient number, since it is larger than the sum of its proper divisors (11229283).

21437661 is a wasteful number, since it uses less digits than its factorization.

21437661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1020851.

The product of its digits is 6048, while the sum is 30.

The square root of 21437661 is about 4630.0821806961. The cubic root of 21437661 is about 277.7958795255.

The spelling of 21437661 in words is "twenty-one million, four hundred thirty-seven thousand, six hundred sixty-one".