21972553 has 2 divisors, whose sum is σ = 21972554. Its totient is φ = 21972552.

The previous prime is 21972539. The next prime is 21972593. The reversal of 21972553 is 35527912.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21790224 + 182329 = 4668^2 + 427^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21972553 is a prime.

It is equal to p_1387654 and since 21972553 and 1387654 have the same sum of digits, it is a Honaker prime.

It is not a weakly prime, because it can be changed into another prime (21972593) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10986276 + 10986277.

It is an arithmetic number, because the mean of its divisors is an integer number (10986277).

Almost surely, 2^21972553 is an apocalyptic number.

It is an amenable number.

21972553 is a deficient number, since it is larger than the sum of its proper divisors (1).

21972553 is an equidigital number, since it uses as much as digits as its factorization.

21972553 is an evil number, because the sum of its binary digits is even.

The product of its digits is 18900, while the sum is 34.

The square root of 21972553 is about 4687.4889866537. The cubic root of 21972553 is about 280.0873579462.

The spelling of 21972553 in words is "twenty-one million, nine hundred seventy-two thousand, five hundred fifty-three".