21997507 has 32 divisors (see below), whose sum is σ = 28200960. Its totient is φ = 16727040.

The previous prime is 21997487. The next prime is 21997513. The reversal of 21997507 is 70579912.

It is a cyclic number.

It is not a de Polignac number, because 21997507 - 2⁷ = 21997379 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21997507.

It is not an unprimeable number, because it can be changed into a prime (21997517) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 247119 + ... + 247207.

It is an arithmetic number, because the mean of its divisors is an integer number (881280).

Almost surely, 2^21997507 is an apocalyptic number.

21997507 is a deficient number, since it is larger than the sum of its proper divisors (6203453).

21997507 is a wasteful number, since it uses less digits than its factorization.

21997507 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 211.

The product of its (nonzero) digits is 39690, while the sum is 40.

The square root of 21997507 is about 4690.1499976014. The cubic root of 21997507 is about 280.1933485990.

The spelling of 21997507 in words is "twenty-one million, nine hundred ninety-seven thousand, five hundred seven".