21907997 has 8 divisors (see below), whose sum is σ = 22241856. Its totient is φ = 21576672.

The previous prime is 21907961. The next prime is 21908039. The reversal of 21907997 is 79970912.

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 21907997 - 2¹² = 21903901 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 (21907927) 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, 22913 + ... + 23849.

It is an arithmetic number, because the mean of its divisors is an integer number (2780232).

Almost surely, 2^21907997 is an apocalyptic number.

It is an amenable number.

21907997 is a deficient number, since it is larger than the sum of its proper divisors (333859).

21907997 is a wasteful number, since it uses less digits than its factorization.

21907997 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1267.

The product of its (nonzero) digits is 71442, while the sum is 44.

The square root of 21907997 is about 4680.5979318886. The cubic root of 21907997 is about 279.8127872693.

The spelling of 21907997 in words is "twenty-one million, nine hundred seven thousand, nine hundred ninety-seven".