21810997 has 8 divisors (see below), whose sum is σ = 23609600. Its totient is φ = 20029680.

The previous prime is 21810991. The next prime is 21811001. The reversal of 21810997 is 79901812.

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

It is a cyclic number.

It is not a de Polignac number, because 21810997 - 2¹⁹ = 21286709 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 (21810991) 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, 1629 + ... + 6802.

It is an arithmetic number, because the mean of its divisors is an integer number (2951200).

Almost surely, 2^21810997 is an apocalyptic number.

It is an amenable number.

21810997 is a deficient number, since it is larger than the sum of its proper divisors (1798603).

21810997 is a wasteful number, since it uses less digits than its factorization.

21810997 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8643.

The product of its (nonzero) digits is 9072, while the sum is 37.

The square root of 21810997 is about 4670.2245128045. The cubic root of 21810997 is about 279.3992092656.

The spelling of 21810997 in words is "twenty-one million, eight hundred ten thousand, nine hundred ninety-seven".