21972407 has 2 divisors, whose sum is σ = 21972408. Its totient is φ = 21972406.

The previous prime is 21972373. The next prime is 21972421. The reversal of 21972407 is 70427912.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21972407 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21972437) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10986203 + 10986204.

It is an arithmetic number, because the mean of its divisors is an integer number (10986204).

Almost surely, 2^21972407 is an apocalyptic number.

21972407 is a deficient number, since it is larger than the sum of its proper divisors (1).

21972407 is an equidigital number, since it uses as much as digits as its factorization.

21972407 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 7056, while the sum is 32.

The square root of 21972407 is about 4687.4734132579. The cubic root of 21972407 is about 280.0867375837.

The spelling of 21972407 in words is "twenty-one million, nine hundred seventy-two thousand, four hundred seven".