123021551 has 2 divisors, whose sum is σ = 123021552. Its totient is φ = 123021550.

The previous prime is 123021539. The next prime is 123021553. The reversal of 123021551 is 155120321.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-123021551 is a prime.

Together with 123021553, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (123021553) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 61510775 + 61510776.

It is an arithmetic number, because the mean of its divisors is an integer number (61510776).

Almost surely, 2^123021551 is an apocalyptic number.

123021551 is a deficient number, since it is larger than the sum of its proper divisors (1).

123021551 is an equidigital number, since it uses as much as digits as its factorization.

123021551 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 300, while the sum is 20.

The square root of 123021551 is about 11091.5080579694. The cubic root of 123021551 is about 497.3480269461.

Adding to 123021551 its reverse (155120321), we get a palindrome (278141872).

The spelling of 123021551 in words is "one hundred twenty-three million, twenty-one thousand, five hundred fifty-one".