21451957 has 2 divisors, whose sum is σ = 21451958. Its totient is φ = 21451956.

The previous prime is 21451949. The next prime is 21451973. The reversal of 21451957 is 75915412.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 15256836 + 6195121 = 3906^2 + 2489^2 .

It is a cyclic number.

It is not a de Polignac number, because 21451957 - 2³ = 21451949 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21451357) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10725978 + 10725979.

It is an arithmetic number, because the mean of its divisors is an integer number (10725979).

Almost surely, 2^21451957 is an apocalyptic number.

It is an amenable number.

21451957 is a deficient number, since it is larger than the sum of its proper divisors (1).

21451957 is an equidigital number, since it uses as much as digits as its factorization.

21451957 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 12600, while the sum is 34.

The square root of 21451957 is about 4631.6257404933. The cubic root of 21451957 is about 277.8576164758.

The spelling of 21451957 in words is "twenty-one million, four hundred fifty-one thousand, nine hundred fifty-seven".