172121661 has 12 divisors (see below), whose sum is σ = 253910592. Its totient is φ = 112306056.

The previous prime is 172121659. The next prime is 172121681. The reversal of 172121661 is 166121271.

It is a happy number.

172121661 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is not a de Polignac number, because 172121661 - 2¹ = 172121659 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (172121611) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 203031 + ... + 203876.

It is an arithmetic number, because the mean of its divisors is an integer number (21159216).

Almost surely, 2^172121661 is an apocalyptic number.

It is an amenable number.

172121661 is a deficient number, since it is larger than the sum of its proper divisors (81788931).

172121661 is a wasteful number, since it uses less digits than its factorization.

172121661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 406960 (or 406957 counting only the distinct ones).

The product of its digits is 1008, while the sum is 27.

The square root of 172121661 is about 13119.5145108346. The cubic root of 172121661 is about 556.2608684322.

The spelling of 172121661 in words is "one hundred seventy-two million, one hundred twenty-one thousand, six hundred sixty-one".