102123821 has 4 divisors (see below), whose sum is σ = 103798044. Its totient is φ = 100449600.

The previous prime is 102123817. The next prime is 102123823. The reversal of 102123821 is 128321201.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 26677225 + 75446596 = 5165^2 + 8686^2 .

It is a cyclic number.

It is not a de Polignac number, because 102123821 - 2² = 102123817 is a prime.

It is a super-4 number, since 4×102123821⁴ (a number of 33 digits) contains 4444 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 102123793 and 102123802.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (102123823) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 837020 + ... + 837141.

It is an arithmetic number, because the mean of its divisors is an integer number (25949511).

Almost surely, 2^102123821 is an apocalyptic number.

It is an amenable number.

102123821 is a deficient number, since it is larger than the sum of its proper divisors (1674223).

102123821 is an equidigital number, since it uses as much as digits as its factorization.

102123821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1674222.

The product of its (nonzero) digits is 192, while the sum is 20.

The square root of 102123821 is about 10105.6331320704. The cubic root of 102123821 is about 467.4218592648.

It can be divided in two parts, 1021 and 23821, that added together give a palindrome (24842).

The spelling of 102123821 in words is "one hundred two million, one hundred twenty-three thousand, eight hundred twenty-one".