157218821 has 4 divisors (see below), whose sum is σ = 158610252. Its totient is φ = 155827392.

The previous prime is 157218797. The next prime is 157218827. The reversal of 157218821 is 128812751.

157218821 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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 32092225 + 125126596 = 5665^2 + 11186^2 .

It is a cyclic number.

It is not a de Polignac number, because 157218821 - 2⁶ = 157218757 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (157218827) 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, 695546 + ... + 695771.

It is an arithmetic number, because the mean of its divisors is an integer number (39652563).

Almost surely, 2^157218821 is an apocalyptic number.

It is an amenable number.

157218821 is a deficient number, since it is larger than the sum of its proper divisors (1391431).

157218821 is a wasteful number, since it uses less digits than its factorization.

157218821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1391430.

The product of its digits is 8960, while the sum is 35.

The square root of 157218821 is about 12538.6929542118. The cubic root of 157218821 is about 539.7195857773.

It can be divided in two parts, 15721 and 8821, that added together give a palindrome (24542).

The spelling of 157218821 in words is "one hundred fifty-seven million, two hundred eighteen thousand, eight hundred twenty-one".